Preheat the oven to 180 C (160 C fan-forced), and line a tray with baking paper.
Cream butter and sugar until light and fluffy. Add egg yolks, vanilla and lemon extract and beat until combined.
Mix together flour, cornflour, baking powder and salt in a small bowl, then mix into the butter mixture until fully incorporated. Fold in the white chocolate.
Roll 2 tbsp sizes balls and place onto the tray, pressing flat slightly. Bake for 12-15 minutes or until lightly golden on the edges. Cool on a wire rack.
Notes
This recipe is adapted from the source above to resemble closely the Coles lemon and white chocolate chunk cookies that have since been discontinued.
You can get lemon extract from Woolworths in Australia, although stock is limited so you may need to call ahead.
These cookies hardly spread at all on the tray, so you can place them close together.
If you can’t get any lemon extract, you can use the zest from a lemon and the juice from half of that lemon instead.
