- Unsalted butter, room temperature for molds
- 1/4 cup unsweetened cocoa powder, plus more for molds
- 1/2 cup all-purpose flour
- 1/2 cup sugar
- 1/4 teaspoon baking soda
- 1/4 teaspoon baking powder
- 1/4 teaspoon salt
- 1 large egg yolk
- 1/4 cup warm water (110 degrees F)
- 1/4 cup buttermilk
- 2 tablespoons vegetable oil
- 1/2 teaspoon pure vanilla extract
- Black Swiss Meringue
- 1/4 cup black sprinkles
- Black Italian Meringue Buttercream
- Preheat oven to 350 degrees. Butter six 1 1/2-by-3-inch dome flexible baking molds, and dust with cocoa, tapping out any excess. Set aside on a baking sheet.
- In the bowl of an electric mixer, sift together cocoa, flour, sugar, baking soda, baking powder, and salt.
- Add egg yolk, the warm water, the buttermilk, oil, and vanilla to the flour mixture. Using the paddle attachment, mix on low speed until smooth, about 2 minutes, scraping the sides and bottom as necessary.
- Pour batter to within 1/4 inch from the top of each mold. Bake, rotating once, until a wooden skewer inserted in center comes out clean, about 25 minutes.
- Invert and unmold cakes onto a wire rack; set aside until completely cool, about 30 minutes. Trim cakes flush with the top of the molds, using a serrated knife.
- To create the heads and legs: Fill a medium pastry bag fitted with a coupler with black meringue. Using a #7 pastry tip for the heads and a #4 pastry tip for the legs, pipe directly onto a parchment-lined baking sheet, keeping the pastry bag at a 45-degree angle to the baking sheet. After piping the heads, carefully affix sprinkles for eyes and mouths. Transfer to oven, bake at 350 degrees.for 5 minutes; set aside.
- Using an offset spatula, spread black buttercream over each cake to evenly coat. Cover with black sprinkles; set aside.
- Transfer the remaining buttercream to a small disposable pastry bag; snip off the end to make a small hole for piping. Carefully pipe a small amount of icing onto the end of one of the spider legs, and attach to one of the spider-body cakes; apply a small amount of pressure to insert the leg into the frosted body. Repeat with remaining legs and cakes.
- Pipe a small amount of buttercream onto the front of one of the bodies, and carefully attach the head. Allow to set; carefully transfer to serving plate by sliding a large spatula under the body from the back of the cake. Repeat with remaining cakes and heads.