Line a baking tray with non-stick baking paper. Preheat oven to 170oC.
Using an electric mixer, beat the butter and brown sugar in a large bowl until thick and creamy. Add egg and vanilla and continue to beat until well combined.
Fold in the plain flour and baking powder until just combined and then add in the white chocolate and nuts. Using your hands, knead until a soft dough is formed.
Roll 1 tbs of mixture into balls and place on the prepared tray. Slightly flatten. Bake for 12-15 minutes or until golden brown. Remove from oven and cool on a wire rack.
Drizzle with extra melted white chocolate for a more indulgent treat!