In the bowl of a food processor with a kneading attachment, add the 550 g of flour, then add 50 g of sugar, the ALSACE LAIT UHT sterilised, semi-skimmed milk, salt, egg yolks and fresh baker's yeast.
Knead for about10 minutes, then add the butter and knead for a further 10 minutes until the dough is soft and smooth.
Dust a mixing bowl with flour.
Roll the dough into a ball and cover with a tea towel.
Leave to rise for 1 hour at room temperature so that it doubles in size.
Knock back the dough, then knead it on a floured work surface.
Divide into 30-g pieces.
Roll the pieces into balls in the palm of your hand.
Line a baking tray with baking paper. Put the balls on the tray, placing them slightly apart.
Cover with a tea towel and leave to rise for 2 hours at room temperature.
Heat the cooking oil in a deep-fat fryer to 180°C. Drop in the doughnut balls and fry until golden brown.
Drain and then roll in the remaining sugar.
Enjoy!