Ever heard of a whoopie pie? They're a bit like a macaroon but with a more cake-like texture. Hugely popular Stateside, the name comes from when Amish women would put them in farmers' lunchboxes and they'd supposedly shout 'whoopie' if they found one in their box!. 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.. 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.. 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.. . .