Wash the oranges hot, grate them dry and peel the skin thinly with a peeler. Roughly chop the peel. Bring 250 ml water, sugar and orange peel to the boil and boil down for 10-15 minutes over a high heat until syrupy.
Spread on a baking tray lined with baking paper. Leave to dry in a preheated oven (electric cooker: 100 °C/ circulating air: 75 °C/ gas: not suitable) for approx. 1 hour. Grind finely in the universal chopper.