Ingredients:

  • 2 cups (250g) all-purpose flour
  • 2 cups (400g) granulated sugar
  • 3/4 cup (75g) black cocoa powder
  • 2 tsp (10g) baking soda
  • 1 tsp (5g) salt
  • 1 cup (240ml) buttermilk
  • 1/2 cup (115g) vegetable oil
  • 2 large eggs
  • 1 cup (240ml) boiling water
  • 1 cup (225g) unsalted butter, softened
  • 3 cups (360g) powdered sugar
  • 1/4 cup (25g) black cocoa powder
  • 2 tbsp (30ml) heavy cream
  • 1 tsp (5ml) vanilla extract
  • 1 cup (250g) marshmallow fluff
  • 1 drop (0.5ml) black gel food coloring
  • 1 chocolate truffle

Instructions:

  1. Preheat oven to 350°F (175°C). Whisk all-purpose flour, granulated sugar, 75g black cocoa powder, baking soda, and salt together.
  2. Add buttermilk, vegetable oil, and eggs to the dry ingredients. Stir in boiling water last until the batter is thin.
  3. Pour batter into two 9-inch round cake pans and bake for 30–35 minutes until a toothpick comes out with moist crumbs. Let cool completely.
  4. Prepare the buttercream by beating softened butter and powdered sugar until light, then folding in 25g black cocoa powder, heavy cream, and vanilla extract.
  5. Apply a thin crumb coat of buttercream to the cake and chill for 30 minutes.
  6. Apply the final smooth layer of buttercream to the top and sides. Chill for 1 hour to firm up.
  7. Warm marshmallow fluff in the microwave for 5–10 seconds and transfer to a piping bag.
  8. Pipe 5–7 straight lines (spokes) from the center to the edge, then pipe concentric circles that curve slightly inward between the spokes to create a web.
  9. Place a chocolate truffle in the center for the spider body and pipe 8 tiny legs using the remaining marshmallow fluff tinted with black gel food coloring.