Berlin doughnut (Berliner)

Instructions

1. Mix the yeast, a spoonful of sugar and the lukewarm milk, then leave to rest for 10 minutes until a foam forms.
2. In a large bowl, mix the flour, the rest of the sugar, the salt and the lemon zest. Make a well in the centre.
3. Add the yeast and milk mixture, the eggs and the soft butter. Knead for 10 minutes until you have a smooth, elastic dough.
4. Cover and leave to rise for 1 hour in a warm place, until it has doubled in size.
5. Knock back the dough, roll it out 1 cm thick and cut out 7 cm discs with a cutter or a glass.
6. Place a small spoonful of jam in the centre of half the discs, then cover with the remaining discs and seal the edges by pinching.
7. Leave the balls to prove for 30 minutes under a tea towel. Heat the oil to 170 °C and fry for 3 to 4 minutes per side, turning them carefully.
8. Drain on kitchen paper, then roll them in sugar while still warm.