Christmas Tree Cupcakes

Preheat oven to 325 degrees. Invert two 9 1/2-by-3-inch disposable round foil baking pans. Using a craft knife or a paring knife, cut six X shapes in bottom of each, spacing them evenly, to make 1 1/2-inch openings. Fit a waffle cone snugly into each opening, standing the cones upright. Line each cone with parchment paper, and then place a dried bean or a hazelnut in bottom to prevent batter from leaking. Place pans and cones on parchment-lined baking sheets. Line a 12-cup mini-muffin tin with paper liners.

Whisk together cocoa powder, flour, sugar, baking soda, baking powder, and salt in a large bowl. Whisk together eggs, warm water, buttermilk, oil, and vanilla in a medium bowl. With a mixer on low speed, gradually add egg mixture to flour mixture, beating until just combined. Raise speed to medium, and beat for 3 minutes. Carefully pour batter into cones, filling each two-thirds full. Spoon 1 1/2 tablespoons batter into each muffin cup (these will be the tree bases).

Bake until a skewer inserted into center of cake comes out clean, 15 to 18 minutes for cupcakes and 35 minutes for cones. Let cakes cool on a wire rack for 15 minutes. Remove cakes from cones and parchment. Let cool completely on the rack.

If necessary, use a serrated knife to trim top of each cupcake to create a flat surface. Place a dab of frosting on top of each cupcake, and position a cone cake on top. Place frosting in a pastry bag fitted with a small star tip (such as Ateco #19) and pipe frosting decoratively all over tree. Sprinkle with sanding sugar. Top each tree with a mini gingerbread star, if desired. Trees can be refrigerated, uncovered, for up to 6 hours before serving.