Double chocolate chip muffins

100g    Butter, Softened
125g    Caster sugar
100g    Brown sugar
2          Eggs
150ml   Sour cream
5tbspn  Milk
250g     Plain flour
2tbspn  Bicarb soda
2tbspn  Cocoa powder
200g     Dark choc chips

1. Preheat the oven to 190degC. 
2. In a large bowl beat butter and sugars until light and fluffy.
3. Beat in the eggs, sour cream & milk until well combined.
4. In a separate bowl sift the flour, bicarb and cocoa then fold into the creamy mixture. 
5. Fold in choc chips
6. Divide into a 12 cup muffin mould and bake for 20-30mins. 
7. Leave to cool for 5 mins then transfer to a cooling rack.