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I knew bolo bao were a beloved confection in Hong Kong (and beyond), but I was still blown away at the response my Bolo Bao Cookies got when I posted a couple weeks ago.
As a recap, bolo bao are also known as “pineapple buns” due to their crackled topping, which apparently looks pineapple skin to some, and confusingly not because they contain any of the tropical fruit. In fact, these buns feature an egg-yolk flavored and colored crumbly topping so their overall flavor profile contains stronger notes of vanilla than anything else.
As a quick aside, if you’ve ever noticed that bolo bao bear striking similarity to another cookie-topped bread confection, Mexican conches, then you might not be surprised to hear that the two are very closely related cousins and that the bolo bao descended from the Concha in the early 20th century, but that’s a post for another time.
Anyway, after posting the bolo cookies, a few people wondered aloud in my comments whether something similar could be done to croissants. I’m admittedly not a fan of many of the cream-stuffed croissants that you can find at many cafes these days thanks in large part to the likes of Mr. Holmes Bakehouse. Typically if I’m eating a croissant, I want it to be light, buttery, and flaky, not filled with heavy custard (no hate to those who do like them — they’re just not for me!). And, I typically skew cynical when it comes to fusion foods — though this is a disposition I’m trying to break — so I wasn’t sure whether I actually wanted to test this out.
But my curiosity got the best of me and I set out to give the people what they wanted: the bolo croissant (or bolo bao croissant? I think bolo croissant has a better ring to it)!
I started out following almond croissant methodology, because after all, the almond croissant is, in my eyes, the pinnacle of twice-baked croissant perfection. As I understand it, almond croissants were developed as a way to reduce waste and put day-old croissants to good use. Bakers began dipping these croissants, which had gone kind of stale, into a sugar syrup for moisture, then spreading an almond cream mixture in the middle and on the top of each pastry before baking again. Despite my distaste for custard-filled croissants, I am a huge fan of almond croissants, not least because I’m a huge fan of most things that are almond-flavored.
So during my first attempt, I let my croissants, which I procured from my local cafe Eyes Peeled (who in turn procures their baked goods from Sugar Bloom Bakery, one of my favorite patisseries in LA) go stale for a day before dunking, filling, and topping.
The result, while delicious, fell a bit flat — literally. I suspect this is due to the fact that Hong Kong style custard filling contains a lot more moisture than almond cream filling, so the croissants didn’t stand up well to the dunk. My friend Jenn remarked that she actually liked how the croissants had flattened out a bit, but it just felt like a desecration of my beautiful Sugar Bloom croissants.
The second trial was a hit, though. I changed a few things:
- I used fresh croissants. Day-old should still work, but you definitely don’t need to wait around if you want bolo croissants today.
- I skipped the dunk.
- I reworked the custard recipe to make it smoother and hit the perfect nostalgic flavor I think of when I think of trips to dim sum or HK style bakeries.
- I reworked my shaping and scoring technique for the topping to make it more visually appealing. Since these croissants won’t rise when you bake them, the topping won’t crackle on its own (that crackling comes from the spreading of the bread or cookie dough beneath the topping). So, a grid pattern turned out to be much prettier, even though I typically associate it more with Japanese-style melon pan, and not bolo bao.
And they came out *so good*. So good that even a cynic like me has decided these will probably be a regular part of my baking rotation from now on. A (Cantonese) friend of mine declared these were maybe “the best bolo bao [he had] ever had” — and even though they’re not actually bolo bao I have to say I understand what he means.
I put all my learnings together into a comprehensive guide for you to make your own show-stopping bolo croissants:
Topping
You don’t necessarily need a food process for this step but it makes things much, much quicker. If you don’t have one, you can use a pastry cutter or your fingers. Just work quickly so the butter doesn’t completely melt on you.
Filling
The trick to making a smooth custard is constantly mixing it while it’s cooking and making sure you continue cooking for 2 solid minutes after the mixture starts to boil. This ensures all the starch cooks so you don’t end up with a grainy mouth feel.
Assembly and Baking
After making dozens and dozens of bolo cookies and a few bolo croissants, I figured out the best way to shape and roll bolo topping. The chilling step seems counterintuitive since you end up re-warming the topping with your hands as you knead it, but it’s important for getting the texture right. I did an experiment where I shaped the topping right away without chilling and the topping lost its crumbliness and was overall a little tougher, so don’t skip that step.
I’ve also done experiments with yolk color — if you’re lucky like me and have a place that sells eggs specifically with a dark yolk color, it’ll definitely make a difference here, but is absolutely not necessary. I don’t normally opt for “dark yolk” eggs since it doesn’t technically have a nutritional difference, but for the egg wash it lends a beautiful rich color.
Flattening the topping with the heel of your hand provides an uneven thickness that gives the topping some lovely texture and helps it crack more when used in bao or cookie applications, however these croissants are already baked and won’t rise any more, so adding a grid cross pattern helps make these more visually appealing.
Broiling helps give the croissants a darker, more mottled coloring, which I find attractive, but you’ll need to be very watchful if you do this so you don’t burn them. They’ll also taste great even if you don’t broil.
Specialty Ingredients
- Bird’s Custard Powder — This is essentially a pudding mix that comes from the UK and is a popular ingredient in Hong Kong style bakery treats due to British colonization. It’s not strictly necessary but it lends a very distinct and nostalgic flavor to these pastries. In the US it can be found online or at specialty retailers like Cost Plus World Market. Its main ingredient is corn starch and it doesn’t contain any sugar, so if you need to make a swap you can try an equal part cornstarch and some extra vanilla extract (though I haven’t tried this myself). I’ve also heard American-style vanilla pudding mix can work, but again I haven’t tried myself so I can’t vouch for this swap.
- Salted Egg Yolk — This can take a couple of different forms: whole salted duck eggs, vacuum sealed salted egg yolks on their own, and salted egg yolk paste in a jar. I prefer the latter two options, as whole salted eggs can be annoying to deal with. The first two are commonly found at Chinese supermarkets while the paste is less common. If you don’t have access to a Chinese supermarket where you live, all 3 options should be available from specialty online retailers like YamiBuy. If you can’t find it, just omit from the recipe but increase the salt content by 1/4-1/2 teaspoon, tasting as you go.
Bolo Croissants
Equipment
- 1 food processor
- 1 bench scraper
Ingredients
For the Custard Filling
- 300 g cold milk
- 15 g Custard powder like Bird’s*
- 15 g corn starch
- 120 g granulated sugar
- 1 egg yolk
- 2 tsp salted egg yolk**
- 1 tsp vanilla extract
- Pinch of salt
- 3 Tbsp butter
For the Topping
- 60 g Unsalted Butter cold
- 60 g Sugar
- 2 Egg Yolks
- 1 Tbsp Custard Powder
- 1/2 tsp salt
- 1/2 tsp baking powder
- 120 g all purpose flour
Egg Wash & Assembly
- 6 croissants
- 2 egg yolks
- 2 tsp water
- Pinch of salt
Instructions
Make the Custard Filling
- Add milk, custard powder, and cornstarch to a medium sized pot and whisk well until there are no clumps remaining. Add the sugar and salted egg yolk and whisk again. There may be some small chunks of salted egg yolk remaining, but this is okay.
- Add the (regular) egg yolk, vanilla extract, and salt, and whisk once more to combine.
- Move the pot to the stove and heat on medium, mixing with a flexible spatula constantly so the bottom doesn’t stick or burn, until the mixture thickens. Once the mixture is thick and you see bubbles emerging at the very center of the pot, turn the heat down slightly, keep stirring, and set a timer for 2 minutes. Continue cooking until the 2 minutes is up (this ensures the starch is completely cooked), then remove from heat.
- Stir in the cold butter until it’s melted & fully combined, then transfer the mixture to a small bowl. Press a piece of plastic wrap directly against the surface and refrigerate for at least an hour. This custard can be made ahead of time and kept in the refrigerator for up to 3 days until ready to use.
- When using very cold custard filling, it will firm up quite a bit. Don’t worry, just “smush” and stir it with a spoon or spatula, and it will loosen and return to a velvety texture.
Make the Bolo Topping
- Add butterm sugar, salt, and baking powder to the bowl of a food processor. Blitz until the butter is no longer stiff, but is still cold (don’t over mix at this step).
- Add the custard powder and flour and process until the mixture turns to the texture of a fairly uniform, fine gravel.
- Add the egg yolks and process one more time until you can see the yellow of the yolks fully incorporate.
- Dump the crumbly mixture onto a large piece of plastic wrap. Gently press and knead the mixture to form a crumbly, but cohesive, log. Wrap tightly in plastic wrap and press/roll the log once more to even it out before transferring it to the fridge to chill at least 2 hours. This can be made ahead of time and kept in the fridge for up to 3 days before using. Mixture should also freeze well, though I haven’t done any testing on this.
Assemble and Bake the Croissants
- Preheat oven to 350F.
- Slice croissants in half (like a sandwich). Fill each “sandwich” with about 2 Tbsp of custard filling and gently press with the back of a spoon (or clean hands) to level it out a bit. Replace the top of each croissant.
- Divide the topping mixture into 6 even pieces. Starting with one piece, quickly and firmly press and knead the mixture in your hand until it softens into a pliable dough (though you still want it to be firm/cool to the touch, not melting or sticky). Roll the dough between your hands to form an oblong cylinder shape, about 2-3 inches long.
- On a clean work surface, use the heel of your hand to press the oblong dough cylinder into a shaggy “rectangle” shape (it will be far from a true rectangle, but you want it to be a shape that’s somewhat long and narrow). If the topping becomes really sticky at any point, dust it lightly with some flour.
- Use a bench scraper (or a sturdy metal spatula, or something similar) to scrape the blob shape off your work surface and slide it onto the top of a croissant. No need to press the topping down.
- Repeat this process until all 6 croissants are topped.
- Make the egg wash by combining the egg yolks, water, and salt in a small dish. Brush the the topping of each croissant with this egg wash. You don’t want to brush the croissant itself, only the bolo topping.
- If desired, use a small knife to very lightly score the surface of each bolo piece in a grid shape. The idea is not to cut all the way through the topping — you’re really only trying to score the egg wash.
- Bake croissants for 15-20 minutes until the topping is lightly puffed and golden brown. If desired, after 15 minutes, you can move the croissants under a broiler (only do this if your broiler is on top of your oven, not the bottom) to achieve a darker color. If you do this, be careful to keep a very close eye on the croissants so they don’t burn, which can happen very quickly.
- Remove from oven and let cool slightly before enjoying. These are best enjoyed the day they’re made.