Ingredients:

  • 420g all-purpose flour
  • 100g Dutch-process cocoa powder
  • 1.5 tsp baking powder
  • 1 tsp baking soda
  • 1 tsp salt
  • 170g unsalted butter, room temperature
  • 400g granulated sugar
  • 1 large egg
  • 1 tbsp vanilla extract
  • 240ml buttermilk
  • 215g marshmallow fluff
  • 225g unsalted butter, softened
  • 180g powdered sugar
  • 1 tsp vanilla extract

Instructions:

  1. Preheat your oven to 350°F (175°C) and line baking sheets with parchment paper or silicone mats.
  2. In a medium bowl, sift together the flour, cocoa powder, baking powder, baking soda, and salt.
  3. In a stand mixer, beat 170g of butter and granulated sugar on high for 3 minutes until pale and voluminous.
  4. Add the egg and 1 tablespoon of vanilla extract, beating until the mixture reaches a whipped cream consistency.
  5. Set mixer to low. Add the dry ingredient mixture in three parts, alternating with the buttermilk, mixing only until streaks disappear.
  6. Using a 2-tablespoon cookie scoop, drop batter onto prepared sheets. Bake for 10 minutes until domes are springy. Transfer to a wire rack to cool completely.
  7. Prepare the filling by beating the remaining 225g of butter, marshmallow fluff, powdered sugar, and 1 teaspoon of vanilla until aerated and fluffy.
  8. Spread or pipe a generous amount of filling onto the flat side of one cooled cake and top with another to create a sandwich.