Preheat oven to 150ºC or 130ºC fan. Spread nuts on a baking tray and cook for 7-8 mins, or until lightly golden. Cool and chop.
Use electric beaters to beat butter and sugar until light and creamy. Add sifted flours and use a butter knife to mix together, then add the ginger and macadamias and mix in.
Gather dough together and turn out onto a sheet of non-stick baking paper. Press dough out to a 25cm round. With dough still on the paper, lift it onto a baking tray and use your fingers to pinch the edges to give a fluted effect. Score dough into wedges and prick with a fork. Sprinkle with extra sugar.
Cook for 35 mins, or until firm and pale golden. Cool on tray, dust with icing sugar, then cut into wedges.