I used the Wilton mini whoopie pie pan to make the cake circles. I actually used a box mix for the cake - I like Orgran's gf vanilla but sub out the egg with 1/2 c pear sauce or applesauce plus 1/2 tsp baking powder. The orange buttercream is 1 stick of butter/margarine plus 1 pound of powdered sugar, 1 tsp vanilla, and about 4 tbsp of orange juice - adjust the liquid for a soft frosting. I bought the plastic tubes on Amazon, but Wilton makes ones now too. To assemble, you push a cake circle...