The blue and green whoopie pies are lovely but the red food colouring is a bit overpowering.
125g unsalted butter, softened
200g caster sugar
350g plain flour
1 tsp bicarbonate soda
food colouring of your choice
Add the dry ingredients together with the egg. Add the buttermilk a bit at a time and mix until it's smooth and seperate into bowls for however many colours you want to do and plonk (yes, plonk!) onto a baking tray roughly 5cm apart and bake for 10-15 mins.
I filled mine with buttericing but you can fill them with anything you like, even chocolate, mmmmmm!