Pineapple Chocolate Muffins

The first muffins of the new year were these ones. Chosen because I fancied pineapple muffins, and I knew that the electrician would go for chocolate - but it works as a combination.

In a large bowl sieve together:
50g cocoa powder
300g self-raising flour
Stir in:
220g caster sugar

In a small bowl mix together:
90g melted butter
half cup sour cream
three quarter cup juice (Drained from a can of crushed pineapple)
1 large egg

Mix the wet into the dry then stir in:
1 cup drained crushed pineapple

Divide the mixture between 12 muffin cases
Bake on 190 degrees for 20-25 minutes
Leave in the tin for a few minutes before moving onto a wire rack to cool