Boil up the milk. Let polenta trickle in and simmer for about 2 minutes while stirring. Pour into a bowl, let it cool down, stirring more often.
For the compote, bring the nectar and 4 tablespoons of sugar to the boil. Stir starch with 3 tablespoons of water until smooth. Stir into the boiling nectar and simmer for about 2 minutes. Stir in frozen berries and put the compote aside.
Preheat oven (electric cooker: 175 °C/circulating air: 150 °C/gas: see manufacturer). Grease a springform pan (26 cm Ø). Rinse orange with hot water, dab dry. Finely grate the orange peel. 1⁄2 Squeeze the orange.
Separate eggs. Beat the egg white with 1 pinch of salt until stiff. Sprinkle 100 g sugar and continue stirring for about 3 minutes. Stir the egg yolk, orange peel and orange juice into the polenta. Fold in the beaten egg white. Pour the polenta mixture into the mould and smooth it down.
Bake in a hot oven for about 50 minutes. Let it cool down. Dust with icing sugar for serving. Add berry compote.