Flourless pistachio, almond, orange and chocolate muffins

Very soft, without flour or baking powder, suitable for coeliacs and others!
INGREDIENTS FOR 12 MUFFINS
1 preferably organic orange
100 g brown sugar
70 g pistachios
40 g almonds
3 eggs
50 g dark chocolate
I wash orange thoroughly and boil in water for 10 minutes.
I chop dark chocolate., cut cooled orange into pieces and put in processor, removing seeds.
I blend orange into purée.
I chop pistachios and almonds, not too finely.
I separate yolks.
From whites.
I whisk yolks and brown sugar until pale and thick.
I mix in orange purée.
I add chopped nuts, reserving a generous tablespoon.mix.
I add chopped chocolate.
I whisk whites stiff.
I vigorously mix a little in, then gently fold in the rest upwards from the bottom.
Everything should be combined.
I line a muffin tin with cases and spoon in mixture., add reserved chopped nuts.
I bake at 180°C for about 25/30 minutes, depending on oven, remove cooked muffins, cool and dust with vanilla icing sugar.
From Il Cucchiaio d'Argento, originally pistachios only. I made a small change with excellent results.