Preheat the oven to 375F/190C, 10 minutes before baking. Grease 10 - 12 muffin cups or use paper cases. With an electric mixer, cream the butter until soft. Add both sugars and beat until light & fluffy. Beat in the eggs 1 at a time. Sift together the flour & baking powder, twice. Fold into the butter mixture, alternating with the milk.

Divide half the mixture between the muffin cups. Sprinkle several chocolate chips on top, then cover with a spoonful of the batter. To ensure even baking, half fill any empty cups with water. Bake until lightly coloured, about 25 minutes. let stand 5 minutes before turning out.