Triple Chocolate Muffins

Tim's favourite, and being as he is popping by tomorrow I thought I had ought to oblige, particularly being as he still hasn't had his birthday present from me yet - whoops. I do hope these will make up for the delay.

In a large bowl sift together:
300g self-raising flour
50g cocoa powder

Stir in:
220g caster sugar

In a small bowl mix together:
90g melted salted butter
half cup sour cream
three quarters cup milk
vanilla essence
1 large egg

Mix the wet into the dry ingredients then stir in:
100g white chocolate chunks
100g milk chocolate chunks

Divide the mixture between 12 muffin cases
Bake on Gas 5/6 for 20-25 minutes
Leave in the tin for a few minutes before moving onto a wire rack to cool