1. Preheat the oven to 200°C (400°F) Gas 6.
2. Melt the butter and set aside to cool a little.
3. Sift the plain, baking powder and salt into a bowl. Stir in the lavender sugar.
4. In a separate large mixing bowl, stir together the caster sugar and melted butter.
5. Next add the eggs and lemon zest and stir again until smooth. Fold in the flour, then the chopped white chocolate and macadamia nuts, if using. The mixture should now be quite thick.
6. Pour the mixture into the prepared baking pan and level the surface. Bake in the preheated oven for around 20 minutes or until cooked but still slightly squidgy in the middle. Take care not to overbake.
7. Remove from oven and turn out almost immediately to cool on a wire rack.
8. Dust with icing sugar and garnish with additional lavender or chopped nuts if desired. Cut into squares to serve.
Note: For the lavender sugar, I use equal parts food-grade lavender to sugar and pulse it until fine in a spice grinder or food processor, sifting out any large pieces that remain.
Recipe courtesy of SCANDIKITCHEN: FIKA & HYGGE by Bronte Aurell - Published by Ryland Peters & Small – Photography by Peter Cassidy