Lemon and chocolate cake

I made this lovely lemon cake in the Easter holidays and didn't get around to posting the recipe. It's from 'Green and Black's Chocolate Recipes'. We took it for our train journey to Edinburgh, it certainly beat anything you could buy on the train. My favourite lemon cake has to be Nigellas Lemon drizzle cake, which I'll have to do soon. 

Ingredients for batter:

125g unsalted butter

125g caster sugar
2 large eggs
150g self-raising flour
1 tsp baking powder
grated rind of 1 large lemon
1 tablespoon milk
75g dark chocolate, minimum 60% cocoa solids, chopped

Ingredients for drizzle:
50g golden granulated sugar
juice of one lemon

Preheat the oven to 180C. Line a loaf tin with grease paper.
Whisk the butter, caster sugar, eggs, flour, baking powder and lemon rind for about 2 minutes. Whisk in the milk to make a soft dropping consistency. Stir in the chocolate.
Spoon the mixture into the prepared tin, smooth the surface, bake for 40 minutes or until the centre of the cake springs back when gently pressed. Remove from the oven.
Stir the granulated sugar into the lemon juice and pour over the hot cake in its tin. Make a few holes with a fine skewer if the icing remains on the surface.
Remove the cake from its tin and place on a wire rack, leaving it in it’s paper to cool completely.