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I was first introduced to Blum’s Coffee Crunch Cake in pastry school. It was my assigned recipe during Cake Week. I had never heard of it before then, but it is a beloved treat that originated in San Francisco. It was invented in the 1940’s by Ernest Weil at Blum’s confectionery shop in Union Square, the first of several locations. A staff member overcooked some candy and Ernest smashed it into pieces to decorate the sponge cakes. And thus, the Koffee Krunch Cake (original spelling) was born.
My friend Alison, whom I met in pastry school, invited me to bake with her and we had fun reminiscing about class while baking the cake. After graduating, Alison had a gelato truck and honeycomb was one of the flavors so she’s made a lot of the confection since then. Her tips are included below. Many recipes say the cake is best eaten the day-of, but personally, I liked how the coffee crunch absorbed into the cream, the next day, and got a bit syrupy.
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Blum’s Coffee Crunch Cake
Adapted from Tante Marie Cooking School
Ingredients:
For the cake:
2 1/4 cups cake flour
1 1/2 cups granulated sugar, divided
1 tablespoon baking powder
1 teaspoon kosher salt
1/2 cup vegetable oil
6 large eggs, separated
Zest of 1 lemon
1 tablespoon vanilla extract
For the coffee crunch:
3/4 cup granulated sugar
2 tablespoons strongly brewed coffee, cooled
2 tablespoons light corn syrup
1 1/2 teaspoons baking soda
For the frosting:
1 1/2 cups heavy cream, chilled
1/4 cup strong brewed coffee, cooled
1 teaspoon vanilla extract
3 tablespoons confectioners’ sugar
Directions:
For the cake:
Place the oven rack to the lower third of the oven. Preheat to 325°F.
In a large bowl, whisk together flour, 3/4 cup sugar, baking powder, and salt. Add 3/4 cup water, oil, egg yolks, zest, and vanilla; beat until smooth.
In the bowl of an electric mixer fitted with the whisk attachment, whisk egg whites on medium-high speed. With machine running, add remaining 3/4 cup sugar in a slow steady stream, beating until incorporated and stiff glossy peaks form.
Remove bowl from mixer. Gently but thoroughly, fold beaten egg whites into batter, in two additions. Pour batter into an un-greased 10-inch angel food cake or tube pan with removable bottom. Bake until a toothpick inserted in the center comes out clean, about 55-60 minutes.
Remove the cake from the oven, and invert onto a narrow necked bottle if your pan doesn’t have feet. Let stand until cool, about 1 hour. While the cake cools, prepare the coffee crunch and whipped cream.
For the coffee crunch:
Lightly coat a rimmed baking sheet with neutral oil or use a nonstick cooking mat; set aside.
In a 4-quart saucepan, combine the sugar, coffee, and corn syrup. Cover the pot with the lid and cook over low heat, until sugar has dissolved. When you see steam, carefully remove the lid. The condensation will help to wash down any sugar crystals on the sides of the pan. Then increase heat to medium-high and cook until it reaches 290°F on a candy thermometer. Remove pan from heat. The mixture will continue to cook with the residual heat. You don’t want the temp to go past 310°F.
Sift baking soda evenly over sugar syrup to prevent any clumps in the candy. Whisk just until combined. Careful as the mixture will foam up rapidly. Pour immediately into the center of the prepared baking sheet. Do not spread. Let stand, until cool, about 30 minutes.
Tap the crunch with a spoon or knife handle to crack. Break into irregular 1/4-to-1/2-inch pieces. Some crumbling is okay. That will be used for the inner layers. Set aside until ready to assemble the cake. If not using immediately, place in an airtight container.
For the whipped cream:
In the bowl of an electric mixer fitted with the whisk attachment, whip the cream until medium peaks form. Add coffee and sugar, and beat to combine until stiff peaks. Use immediately.
For the cake assembly:
Once the cake has cooled, loosen it by running a flat metal spatula or knife around the perimeter of the cake and the center where the tube is. Then remove from pan. Use a serrated knife to cut the cake horizontally into 3 even layers. Note: We only did 2 layers in the video but think it would be more flavorful with an extra layer of the whipped cream and honeycomb.
Place one layer on a serving platter. Spread whipped cream about 1/2″ thick. Scatter an even layer of coffee crunch on top. I use the smaller, crumbly pieces for the inner layer so it absorbs into the cream more easily, and save the larger chunks for decorating the outside of the cake. Place the second layer of cake on top and repeat the whipped cream and coffee crunch layers. Then top with the third layer of cake. Frost sides and top of the cake with the remaining cream. Place in the refrigerator until ready to serve.
Just before serving, cover the entire cake generously with coffee crunch. Serve immediately.
Serves 12.