Stir yeast, some lukewarm milk and some sugar in a cup until smooth. Put the rest of the flour, fat, salt, 1 egg and the remaining milk into a mixing bowl and work into a smooth dough using the dough hooks of the hand mixer.
Cover and leave to rise in a warm place for 20 minutes. Wash and halve the nectarines, remove the stone and cut the fruit halves into slices. Bring plum juice and 1/4 litre water to the boil. Whisk cornflour and some cold water, stir into the plum juice and bring to the boil briefly.
Leave the nectarine slices to soak for about 5 minutes at low heat. Let the compote cool down. Knead the yeast dough once again and press it into a greased casserole dish (25 x 35 cm) with moistened hands.
Pull the dough up along the edge of the mould. Spread plum puree on the bottom. Whisk remaining eggs, egg yolks, cream, 2 tablespoons icing sugar and cognac. Pour the egg cream into the mould. Bake Royal in a preheated oven (electric: 175 °C/ gas: level 2) for approx. 50 minutes.
Dust with remaining icing sugar and decorate with mint leaves. Add extra nectarine compote and sprinkle with mint leaves. Serve the nectarine compote separately.