For chocolate pies add 2 tablespoons of cocoa powder to the dry ingredients and sift.
Sift all dry ingredients together and set aside. Cream butter and sugar until light and fluffy. Do not over mix. Mix the egg and vanilla to the butter and sugar. Mix half the dry ingredients followed by half the buttermilk, repeat until everything is uniformly incorporated. Pipe inside a 1 1/4 inch circle drawn on parchment on a cookie sheet.
When piping keep pastry tip about 3/8th away from parchment, after piping, use a damp finger to lightly press down any points that have pulled away from the whoopie disk.
Bake in a preheated 350 degree convection oven for 4 minutes then turn and bake for another 2.
For creme filling: Mix all ingredients together by hand and assemble Whoopee pies.