The texture of these US imports is a cross between a cake and a biscuit. Whoopie pies are filled with marshmallow fluff which makes them guaranteed to be a hit with the kids!. Whoopie Pie (20) 32 minutes. 19 reviews . Here's what all the fuss about Whoopie Pies is about - and this recipe won't disappoint! What could be better than combining chocolate cake, with a creamy filling. Yummy! . Fall in love with this easy recipe for whoopie pies. Two light discs of chocolate sponge sandwich a fluffy vanilla buttercream filling. Perfect for cake sales, packed lunch treats or making friends at the office!. 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.. Chocolate whoopie pies are an American favourite that you can now create at home with this easy to follow, delicious and simple recipe from Jamie Oliver.. While the mini pie halves are baking, prepare the filling by beating the butter in a bowl until pale and creamy. Add the vanilla extract and gradually add the icing sugar until the mixture is light and fluffy..