Ingredients

  • 4 (1 ounce) squares unsweetened baking chocolate
  • 1 cup butter
  • 4 eggs
  • 2 egg whites
  • 2 cups white sugar
  • 1/4 cup strong brewed coffee
  • 2 teaspoons kosher for Passover vanilla flavoring
  • 1 cup potato starch
  • 2 tablespoons potato starch
  • 1/4 cup matzo cake meal
  • 2 tablespoons matzo cake meal
  • 1/4 cup unsweetened cocoa powder
  • 1/2 teaspoon salt
  • 6 ounces semisweet chocolate chips

Method

  • Preheat oven to 350 degrees F (175 degrees C). Grease 2 8x8-inch baking pans.
  • Melt unsweetened chocolate and butter in the top of a double boiler over simmering water; stir to mix well. Beat the eggs and egg whites together in a mixing bowl with an electric mixer on high speed until very fluffy, about 5 minutes. Gently stir the butter and chocolate mixture, sugar, coffee, and vanilla flavoring into the egg mixture, and beat well to combine.
  • Mix together all of the potato starch, all of the matzo cake meal, cocoa powder, and salt in a bowl. Beat the dry ingredients into the chocolate mixture with electric mixer until fluffy and thoroughly combined. Gently fold the chocolate chips into the batter, and divide between the 2 prepared baking dishes.
  • Bake in the preheated oven until a toothpick inserted into the center of a pan shows moist crumbs, 25 to 30 minutes.