Preheat the oven to 350°F. Beat the eggs and sugar until frothy. Add the flour, baking powder, and butter and mix until smooth. Divide the cake batter between 2 bowls.
Add green food coloring to one bowl and red food coloring to the other.
Pour the green cake batter into one greased cake pan, and the red cake batter into another greased cake pan and bake for 35-40 minutes.
Let the cakes cool, level off the tops, and cut off the baked brown crust surrounding the cakes. Cut both cakes in half horizontally so that you are left with 4 equal cake pieces. Use different sized round cookie cutters to cut the cake pieces into 3 circles.
Put the colorful cake rings back together, but alternate the colors, and stack one cake on top of the other.
Prepare the buttercream frosting, spread it over the cake, and refrigerate for 1 hour.
Level the open ends of the waffle cones so they are straight across. Dip the cones in melted chocolate, decorate with sprinkles and sugar pearls, top with fondant stars, and let the chocolate set.
Drizzle melted chocolate around the edge of the cake so that the chocolate flows down. Top the cake with the chocolate Christmas trees.