Coarsely chop orange chocolate and 60 g dark chocolate. Melt the butter and chocolate in a pot at low heat. Separate the eggs. Beat the egg yolks and 50 g sugar with the whisk of the hand mixer for about 8 minutes until creamy. Sift flour on top, add chocolate-butter mixture and stir in. Beat egg whites until stiff and fold in portions. Grease 4 ovenproof moulds (200 ml each) and sprinkle with 2 tablespoons of sugar.
Pour in the soufflé mixture and bake in a preheated oven (electric range: 175 °C/ convection oven: 150 °C/ gas: level 2) for 20-25 minutes. Meanwhile melt 15 g chocolate on a warm water bath, let it cool down a little. Pour into a disposable piping bag, cut off the tip. Wash kumquats thoroughly and cut into slices. Remove the soufflé from the oven, decorate with kumquat slices and chocolate. Serve immediately