• Set your oven to preheat at 350 degrees and line your muffin pans for 24 cupcakes.

For the brownie layer

• For the brownie base, put the butter and chocolate chips in a large microwave-safe bowl. Microwave for short intervals, stirring after each, until the mixture is smooth.
• Mix in the cocoa powder and instant coffee grounds.
• Blend in the sugars, baking powder, and salt until well incorporated.
• Stir in the eggs and additional egg yolk.
• Gradually add the flour, checking for any dry spots.
• Spoon a generous tablespoon of brownie batter into each cupcake liner and press down with the back of a ¼ cup measuring cup.

For the vanilla cupcake layer

• For the cupcake batter, blend the softened butter and sugar in a stand mixer until creamy.
• Incorporate the milk, oil, egg whites, baking powder, salt, and vanilla.
• Gradually add the flour and ensure everything is well mixed.
• If using, mix in the orange food coloring.
• Spoon a tablespoon of the batter over the brownie bases.
• Bake for 18 minutes until slightly browned around the edges and set in the center. Allow to cool completely.

For the buttercream icing

• For the buttercream frosting, combine the softened butter, vanilla, and salt in a stand mixer. Whip until smooth.
• Slowly add in the powdered sugar, with milk if necessary. Beat the frosting on high speed for a minute, then mix again after scraping the sides.
• Transfer the frosting to a piping bag with a large star tip. Decorate each cupcake with a dollop of frosting and immediately add the sprinkles.