To Make Whoopie Pie Filling: Beat egg white and mix with the milk, 1 teaspoon vanilla and 125g of the icing sugar. Mix well then beat in the butter and the remaining sugar. Beat until light and fluffy.. Welcome to Flonga Games! All the games on our site are FREE to play and we launch new games every day. You can play thousands of free online games including action, life, puzzle, skill and sports games.. I have baked 4-6 batches of whoopie pies using recipes from several books. Most of the time the top pie cracked. In some cases, the top pie cracked pretty heavily. Most of the time the top pie cracked.. Find great deals on eBay for whoopie pie baking pan. Shop with confidence.. Heat oven to 180C/160C fan/gas 4 and line baking trays with parchment. Mix flour, cocoa, bicarb, sugar and a pinch of salt. Whisk the egg, oil and buttermilk together, then mix into dry ingredients with 75ml boiling water.. Beat the butter and sugar in an electric mixer on high speed until light and fluffy. Beat in the egg, followed by the vanilla and buttermilk. Reduce speed to low, add dry ingredients and beat until combined..