FOR THE BLACK VELVET CAKE: – 2 1/4 cups cake flour – 2 tbsp unsweetened cocoa powder – 1 tsp baking powder – 1/2 tsp kosher salt – 1/2 cup unsalted butter, room temperature – 1 1/2 cups granulated sugar – 2 large eggs, room temperature – 1 tsp pure vanilla bean paste – 3 tbsp freshly brewed coffee, room temperature – 1/2 cup buttermilk – 1/2 cup half and half – 2 tbsp black food coloring – 1 tsp baking soda – 1 tsp distilled white vinegar FOR THE CHOCOLATE MARSHMALLOW FROSTING: – 1 7-ounce jar marshmallow creme – 2 tbsp unsalted butter, room temperature – 1/2 cup confectioners’ sugar – 2 oz semi-sweet chocolate, melted and slightly cooled – 1 tsp pure vanilla extract – 3 tbsp heavy cream – Black food coloring – Sprinkles for decorating