Heat the oven to 350°F (175°C). I set my fan oven at 165°C.
Cream together the butter and the sugars in an electric mixer.
Add the egg and vanilla and beat together.
Sift together the flour, soda and salt.
Add the flour mixture to the wet ingredients, a bit at a time, blending after each addition until no more flour is visible.
Remove the bowl from the electric mixer and stir in the chocolate chips gently but thoroughly with a wooden spoon.
Drop rounded teaspoonfuls of dough about 2 inches apart on baking sheets.
Bake for 8 to 10 minutes until just beginning to turn golden. (Cookies will still be soft.)
Allow the cookies to cool on the baking sheets for 5 minutes before carefully removing with an egg lifter.
Cool completely on a wire rack before storing in an airtight container.