Double chocolate whoopie pies

Preheat the oven to 200C/fan 180C/gas 6 and line two trays with baking parchment.

Cream the butter and sugar using an electric whisk until smooth and creamy.

Add the egg and beat well.

Mix the vanilla extract into the buttermilk. Add half of this mixture to the butter mixture and beat well until combined.

Mix together the flour, cocoa powder, salt and bicarbonate of soda. Add half of this to the butter mixture and beat well.

Add the rest of the buttermilk mixture and then the rest of the flour mixture, beating after each addition.

Stir in the white chocolate chips.

Drop blobs of the dough (4-5 cm across for large/3-4 cm across for small) onto the baking sheets, leaving about 2 inches between each blob.

Bake the cakes for 10-12 minutes until the tops are puffed and they spring back when touched.

Decorate with chocolate ganache buttercream, chocolate glaze and white chocolate chips.