Preheat the oven to 180°C and line a baking tin with baking parchment.
Cream the butter, sugars and vanilla in a large bowl until light and fluffy.
Add the egg to the mixture and beat in.
Next add the flour and baking powder, mixing everything together with a wooden spoon.
Chuck the chocolate and nuts in and give it a good mix up.
Divide the mixture into 12 equal parts and roll each part into a ball. These should be about the same size as a golf ball. Put these onto the baking tray making sure there is plenty of room for them to spread out as the cook.
Grind a little salt onto the top of each ball and place in the hot oven and bake for 15-20 minutes until golden around and slightly darker around the edges.
Carefully remove the baking tray from the oven and leave the cookies to cool on a wire rack.