Preheat the oven to 180°C (356°F).
Cream the butter and erythritol together.
Add the egg and vanilla extract, and mix well.
Sift in the almond flour and baking powder, and combine.
Add the macadamia nuts and white chocolate to complete the dough.
Shape the dough into rounds and place them on a baking sheet.
Bake at 180°C (356°F) for 12–15 minutes, let cool, and enjoy.