Preheat the oven to 160°C.
Cream the butter and sugars together with a handheld electric mixer until pale and fluffy.
Stir the ground almonds, flour, and orange zest into the mixture until thoroughly combined.
Divide the dough into 18 pieces and roll each into a ball.
Flatten each ball on a floured surface to 1cm thick using a fork or cookie stamp.
Place biscuits on a non-stick baking sheet at least 2.5cm apart.
Bake for 20 to 25 minutes until barely colored.
Cool on the sheet for 10 minutes then transfer to a wire rack.
Sprinkle with additional lavender sugar once completely cooled.