In an electric mixer combine the butter, sugar and brown sugar. Mix on medium speed for several minutes, until light and fluffy.
Add in the lemon zest, vanilla extract, lemon extract (if using) and the egg. Mix well.
In a separate bowl mix together the flour, milk powder, salt, baking powder and baking soda.
Add the flour mixture to the butter mixture and mix until just combined.
Fold in the white chocolate chips.
Drop scoops of dough onto a baking sheet.
Bake at 350 for 9-11 minutes.
Notes
**I make these all the time without the citric acid and they are delicious. If you're looking for your lemon cookies to have lots of lemon flavour AND be tangy, this is the answer.