Introduced by the French, sponge cakes are popular sweets in the Vietnamese repertoire. They're enjoyed plain as a great snack or part of the dessert grazing spread, and can be purchased in most Viet bakeries abroad. However, like with many foods, the cake is often much better when made at home.
When I was a kid (ahem, in the 70s), my mother, sisters and I used to regularly turn out many bánh bông lan, which literally means "blooming orchid cake", a nicer moniker than sponge cake. After we arrived in the US, we were thrilled at the vast and relatively inexpensive supply of refined sugar and butter. We went on a baking binge and scoured libraries and joined Book-of-the-Month clubs to read up on sponge cake recipes.
Week after week, we baked the glorious, airy cakes, which perfumed our home with sweet smells. First they were plain and round, flavored with vanilla. Then we baked them in loaf pans and topped them with a mixture of ground pork and onion for a treat called bánh bông lan thịt. (It sounds weird but it is a known Viet entity and an unusual savory sweet combination! There's another version where you mix chopped dried shrimp and thinly sliced Chinese sweet sausage into the batter too.)
Let's cut to the recipe, which is essentially a French butter sponge cake called biscuit au beurre. Note that most Viet recipes for bánh bông lan sponge cake do not employ butter. It is expensive in Vietnam. And, the French approach sometimes omits the butter too. However, a bit o' butter in the batter yields a slightly richer flavor and creamier texture.
It is a remarkably simple combination of ingredients but the Devil is in the details. Before launching into making the cake, remember these points:
- Use the best ingredients you can afford, like fresh eggs, high quality butter, and pure vanilla.
- Have the ingredients at room temperature.
- Cream of tartar acts as a stabilizer for egg whites; it's stocked in the spice aisle of regular supermarkets.
- Cake flour is lighter and produces tender results since it has lower gluten content. Find it in the flour and starch aisle of regular supermarkets. It's sold in boxes.
- A cheap handheld mixer will do. For Luddites, hand whip using a balloon whisk.
- Use metal bowls to mix in; stainless steel is fine, copper is too pricey.
- Wash and dry the bowls and whisk (or beaters) well before using.
- You will be working quickly so start by readying all the equipment and measuring out all the ingredients.
- This is a non-collapsible soufflé. There's a beaten egg base of yolks and sugar into which you add a beaten egg whites and flour. There's more flour here than in a soufflé, which is why the cake hold up as it cools.
- Master a plain cake first before going off on creative riffs. See the Note and Variation section at the end for details.
Bánh Bông Lan
Makes 1 cake
Start by preparing the pan. Use a 4-cup pan, like a high-sided (with a 2" wall) 8-inch round or square, or an 11" x 17" sponge sheet. To prepare the pan, smear a bit of softened butter to lightly coat the bottom and side. Line the bottom with parchment paper. Smear the parchment paper with a bit more butter. Add ¼ to ½ cup all-purpose flour (depending on the size of the pan) and shake and turn the pan around to coat it. Standing over the sink, invert and tap the pan to remove excess flour. Set aside.
Now put a rack in the lower third position and preheat to 350F. Then, have your mixer (or whisk) and rubber spatula handy. Finally, gather the ingredients and organize yourself so you can move swiftly and smoothly through the process.
For egg yolk batter base:
3 large egg yolks, placed in a metal bowls, about 3-quart capacity
½ cup sugar
1 1/2 teaspoons pure vanilla extract
For egg whites:
3 large egg whites, place in a metal bowl, 2-3-quart capacity
Pinch of salt, non-iodized table salt, preferred
Scant ¼ teaspoon cream of tartar
1 1/2 tablespoons sugar
For finishing the batter:
1/3 cup plus ¼ cup cake flour (such as Swans Down brand) scooped and leveled into a sifter set over a piece of parchment or plate (measure 1/3 cup then measure 1/4 cup for 7/12 cup total!)
3 tablespoons tepid melted, unsalted butter (keep cooled butter on stove to avoid solidification)
1. Start beating the egg yolks in the bowl. Gradually sprinkle in the sugar by the tablespoon to incorporate well. (Do this too fast and the batter will be grainy with sugar.) Continue beating for several minutes, until the mixture is thick, pale yellow, and when you pause and lift the whisk (or beaters), the batter drips down and forms a ribbon that slowly dissolves on the surface. Now, beat in the vanilla. Set aside.
2. Wash and dry the whisk (or beaters) well.
3. Start beating the egg whites. When they are foamy throughout, sprinkle in the salt and cream of tartar. Continue beating until soft peaks form (when the whisk (or beaters) is lifted out of the egg whites, a soft, slightly bent over peak of egg white forms in the bowl). As you beat, the whites will have gone from clear to light grey to solid white. Instead of sliding from the walls of the bowl, they will stick to the bowl.
After soft peaks form, sprinkle in the 1 1/2 tablespoons sugar and continue beating for a couple more minutes to generate stiff egg whites (the peak stands straight when the whisk is lifted from the bowl). The whites will have a sheen.
4. Immediately take a large rubber spatula and plop a ¼ of the egg whites into the egg yolk base. Stir gently to lighten the base. Then plop 1/3 of the remaining whites onto the base. Sift ¼ of the flour on top. Delicately and quickly use the spatula to fold the ingredients together, until they are nearly all incorporated. (To fold, plunge the spatula sideways - like a knife - into the center of the batter, touching bottom. Rapidly bring the spatula to the wall of the bowl and rotate it to scoop up and fold the batter over the whites and flour. Do this several times.)
Repeat with another 1/3 of the remaining whites and 1/3 of the remaining flour. Fold again until almost blended.
Fold in ½ of the remaining whites, ½ of the remaining flour. Fold again until almost blended. Fold in the remaining whites and remaining flour. Fold again until nearly blended. At that point, pour in the melted butter in a circle. Quickly fold it into the batter (do not overblend or the batter will deflate). The finished batter will be pale yellow, very thick, and light feeling.
5. Pour the batter into the prepared cake pan. It should fill to about ¼ inch of the rim. Scoop out extra batter to avoid overflow during baking.
6. Use the spatula to spread the batter out evenly in the pan. Tilt the pan in all direction to slightly push the batter toward the rim. This prevents a domed-center during baking.
7. Gently slide the cake into the oven. Bake for 20 to 25 minutes. The cake will rise slowly and then brown. The cake is done when its puff sinks slightly and the sides show a faint line of shrinkage from the edges of the pan.
8. Remove the cake from the oven and cool on a rack for 15 minutes. (It will deflate and pull away from the pan walls.) Run a knife all around the edge, between the cake and the pan. Invert the cake onto your hand (or back on the rack), give the cake bottom a tap, and then remove the cake pan. Peel off the parchment paper and discard. Invert the cake, top side up, onto the rack. Allow to cool completely (about 1 hour) before eating, filling, or icing.
Notes and Variations
- When baking the cake in advance, slip it into a zip-top bag after it has cooled. Refrigerate it for 2 to 3 days or freeze it for several weeks.
- Finely grated citrus zest may be added to the egg yolk base. Substitute it for the vanilla or work it in along with the vanilla. About 1 1/2 teaspoons will do.
- You may omit the melted butter, if you like a lighter, more spongy, chewier result.
- Sift some ground spice or cocoa powder in with the cake flour for flavor variation.
- See the Christmas Yule Log recipe for an almond tangerine version that's a little richer.
- This sponge cake recipe is the foundation for my strawberry and cream layer cake.