Cream butter and sugar.

Add eggs 2 at a time and beat well for about 10 mins.

Add flour and extract and mix well.

Divide batter in half. Add melted chocolate in one and mix.

In a greased or lined cake pan alternate the batter, 2 tablespoon choco batter with 2 tablespoon white batter.

Bake at 180°C for 1h - 1h30 mins.

Let cool before removing from pan.