Preheat the oven to 170ºC/gas mark 3, and line 2 baking sheets with baking parchment.
Cream together the butter and both sugars until pale then add the egg and vanilla extract and mix together well.
Sift in the flour, salt and bicarbonate of soda and add to the butter sugar mixture and mix thoroughly until a dough forms, then stir in the chocolate chips.
Break off pieces of the dough about one tablespoon in size and roll into balls.
Place these on the baking sheet leaving about 5cm space in between each to allow for them spreading out during baking.
Place in the oven and bake for 15-20 minutes or until the cookies are light golden brown.