Preheat the oven to 180°C.
In a bowl, cream together the unsalted butter and erythritol.
Add the egg and vanilla extract, and mix well.
Add almond flour, baking powder, and salt, and mix to combine.
Stir in the macadamia nuts and white chocolate chips.
Scoop the dough into round shapes and place them on a baking tray.
Bake in the oven at 180°C for 12–15 minutes.
Cool on a wire rack before serving.