Giant Whoopie Pie

Instructions

• Preheat the oven to 350˚F (180˚C). Grease and line 2 10-inch (25 cm) round cake pans with parchment paper.
• Make the whoopie pie: In a large bowl, whisk together the flour, cocoa powder, espresso powder, salt, baking soda, and brown sugar, making sure there are no lumps.
• Make a well in the center of the dry ingredients, then pour in the water, vinegar, vanilla and oil to the well. Whisk to combine, working slowly to avoid clumps.
• Scoop 2½ cups (600 g) of batter into the center of each cake pan. Use an offset spatula or a knife to spread the edges of the batter just to the edges of the pans. Do not level the top of the cake, to help create a domed shape.
• Bake for 30 minutes, or until a toothpick inserted in the center of the cakes comes out clean. Let cool in the pans for 10 minutes, then carefully transfer to a wire rack to cool completely.
• Make the filling: In a large bowl, combine the butter and marshmallow fluff and cream with an electric hand mixer for 2–3 minutes, until fully combined. Sift in the powdered sugar, then beat for another 2–3 minutes, until light and fluffy. Transfer the filling to a piping bag or zip-top bag. Cut a 2-inch (5 cm) wide opening on a corner.
• Invert a cake onto a serving platter so the domed side is facing down. Pipe a thick spiral of filling onto the cake, leaving a ¼-inch (½ cm) border around the edge, and smooth with an offset spatula. Place the remaining cake on top of the filling, domed side up, and push down slightly to attach.
• Slice and serve.
• Enjoy!