Insure butter is at room temperature, you can always melt slightly in the microwave, add sugars and mix until creamed followed by egg and vanilla essence. Mix well until light and creamy. Pre heat over at 180 or gas mark 4
Sift flour, salt and baking powder into the creamed mixture. Mix until all the flour is blended and the mixture is now a dough.
Break the chocolate bars (cooking chocolate is recommended) into large chunks, approx 1cm cubes. Add to the cookie dough and mix with hands.
Roll the dough into walnut size balls and place on baking tray covered with baking paper. Place in the oven on the middle shelf.
Cookie bottoms can burn easily so place another baking tray on the shelf below. Bake for 10 mins
Remove from oven and leave to harden for 5 minutes before transferring to wire rack.