Polish doughnuts (Pączki)

step 1 To make the leaven, mix the yeast with the sugar and flour, and stir in the warm milk. Set aside in a warm place for 30 minutes.

step 2 For the dough, put egg yolks into a heatproof bowl and add the sugar and vanilla sugar. Set the bowl over a pan of simmering water and whisk until smooth and thick.

step 3 Sift the flour into the bowl of a stand mixer, add the beaten yolks and the warm cream, mix thoroughly, then add a pinch of salt and the leaven. Bring together to make a dough and knead for 10 minutes (or 15-20 if doing this by hand).

step 4 When the dough stops sticking to your hands, pour in the cooled melted butter and knead for a few more minutes. Cover with a cloth and leave in a warm place to rise for at least 1 hr-1 hr 30 mins.