Heat the oven to 190C/fan170C/gas 5 and line two baking sheets with non-stick baking paper. Put 150g softened salted butter, 80g light brown sugar and 80g granulated sugar into a bowl and beat until creamy.
Beat in 2 tsp vanilla extract and 1 large egg.
Sift 225g plain flour, ½ tsp bicarbonate of soda and ¼ tsp salt into the bowl and mix it in with a wooden spoon.
Add 200g plain chocolate chips or chunks and stir well.
Use a teaspoon to make small scoops of the mixture, spacing them well apart on the baking trays. This mixture should make about 30 cookies.
Bake for 8–10 mins until they are light brown on the edges and still slightly soft in the centre if you press them.
Leave on the tray for a couple of mins to set and then lift onto a rack