By the time I moved to San Francisco Blum's pastry shops had been long closed, but their desserts continued to live on. My sister told me about their most famous creation, Coffee Crunch Cake, and brought me a slice from Yasukochi's Sweet Stop in Japantown.
Coffee-flavored desserts aren't really a favorite of mine, but the combination of sponge-y lemon scented vanilla cake frosted with whipped cream and covered with light, airy honeycomb textured coffee candy was divine. I had to see if I could make it for myself.
Luckily I didn't have any trouble finding a recipe online, one that was originally published in the San Francisco Chronicle. Overall the cake was delicious and very well-received. The only adjustments for next time would be to make an oil-based chiffon for the cake and to use stronger coffee, like espresso, for the coffee flavor to really come through in the crunch.
Blum's Coffee Crunch Cake
Makes one 10-inch cake
1 -1/4 cups cake flour, sifted
1-1/2 cups sugar, divided
1/2 teaspoon salt
6 egg yolks
1/4 cup water
1 cup egg whites (6-8 large eggs)
1 teaspoon cream of tartar
1 teaspoon vanilla extract
1 tablespoon fresh lemon juice
1 teaspoon grated lemon zest
1 tablespoon baking soda, sifted
1/4 cup strong brewed coffee (I recommend espresso)
1-1/2 cups sugar
1/4 cup light corn syrup
2 cups heavy cream
2 tablespoons sugar
2 teaspoons vanilla extract
For the cake:
Adjust rack in the lower third of oven; preheat to 350°F. Sift flour, 3/4 cup sugar, and salt onto a sheet of wax paper; set aside.
Using an electric mixer, beat egg yolks with 1/4 cup sugar until thick and pale yellow. Add water and beat until thickened, about 4 minutes.
Whisk egg whites in bowl of a heavy-duty mixer just until frothy. Add cream of tartar; whisk until soft peaks form. Add remaining 1/2 cup sugar in a steady stream, whisking until thicker, stiffer, glossy peaks form – about 2 to 3 minutes. Whisk in vanilla, lemon juice, and lemon zest. Pour yolk mixture over whites. Fold together with a rubber spatula. Sprinkle a third of the flour mixture over the egg mixture; fold to combine. Repeat two more times just until ingredients are incorporated.
Gently pour batter into an ungreased 10-inch round tube pan with a removable bottom (such as an angel food pan). Level top with a spatula.
Bake for 50 to 55 minutes, or until top springs back slightly when lightly touched. Invert pan over a long-necked bottle to cool for about 45 minutes.
To remove cake from pan, slip a flexible metal spatula down one side of pan; slowly trace perimeter to release the cake. When sides are free, push up on bottom to release cake. Tilt cake with removable bottom still attached, and gently tap bottom against counter to loosen cake. Rotate cake, tapping a few more times, until it appears free. Cover cake with a rack and invert; remove bottom of pan.
For the coffee crunch:
Generously oil a large baking sheet or line with a silicon mat or parchment paper; sift baking soda onto a sheet of wax paper; set nearby.
Combine coffee, sugar and corn syrup in a heavy, 4-quart saucepan. Place over medium-low heat, stirring occasionally, until sugar dissolves. When mixture is clear and begins to boil, increase heat to medium-high; cook until mixture reaches 290°F on a candy thermometer. Toward end of cooking (around 270°-280°), stir occasionally to prevent mixture from scorching and becoming too foamy.
Remove from heat and stir in baking soda (mixture will foam up fiercely). While still foaming, pour out onto prepared baking sheet. Do not spread; let cool undisturbed for at least 1 hour.
Crush into very small pieces. (Place between two sheets of wax paper or inside a freezer size ziplock bag and tap with a rolling pin). Store in an airtight container
For the frosting:
Combine cream, sugar and vanilla. Whisk until cream holds soft peaks.
Slice cooled cake into 3 equal layers using a serrated knife. Spread whipped cream between each layer, carefully stacking layers. Spread remaining whipped cream over the top and sides of cake.
Refrigerate. Just before serving, generously sprinkle top and sides with the coffee crunch