Preheat the oven to 200°C. Grease 10 friand or 80ml muffin pans with butter.
Melt the butter in a saucepan and simmer gently until it deepens in colour. Remove from heat and leave to cool for 5 minutes.
Grind macadamias and icing sugar together in a blender and place in a mixing bowl. Stir through flour. Stir in the egg whites (don’t beat them) and mix to make a soft batter. Pour the melted butter through a fine sieve into the batter and mix thoroughly. Spoon the mixture into the tins to fill about three-quarters full.
Bake for 5 minutes at 200°C then lower oven temperature to 180°C and bake for a further 20–25 minutes, covering the cakes if they get too brown.
Turn the oven off and leave the friands inside for 5 minutes. Cool slightly in the tin and then turn onto a rack. Brush each friand with warm syrup making sure you brush into the crevices. When cool, store in an airtight tin.
Syrup. Combine lime juice and sugar in a pan and bring to the boil, stirring until dissolved.TIP: Oranges or lemons can be substituted for the limes.