Ingredients 
120g butter, room temperature
70g soft light brown sugar
50g caster sugar
200g plain flour
½ tsp baking powder
Salt
1 egg
1 tsp vanilla bean paste or extract
100g white chocolate chunks

Method
Heat the oven to 180c.  Line 2 baking trays with silpat liner or baking parchment.  (Alternatively do I as often do, cook half and freeze half - these cook perfectly from frozen)

Mix the baking powder and salt through the flour.

Beat together the butter and both sugars until soft and combined.

Add the egg and vanilla and beat until completely incorporated.  Add the flour mix and beat again until just incorporated.  Add the white chocolate chunks and briefly mix through. Divide the mixture into 10 equal sized amounts and roll into balls. 

Put the dough balls on the baking tray making sure they have room around them because they spread,  cook for around 10 minutes until the edges are golden.  Leave to cool and harden.