Preheat oven to 170°C. Cream the butter and sugars for at least 5 minutes until the mixture becomes light and fluffy.
Add the egg and vanilla extract and beat well.
Add choc chips, flour, baking soda and baking powder. Beat on low speed until just combined (don’t overwork the mixture or it can become tough).
Press the majority of the dough into the middle of a 23cm/9" round greased springform tin. I baked the leftover dough into 6 small cookies, for decorating or for eating ;)
Bake in the oven for 15 minutes or until lightly golden brown.
Allow to cool completely.