ready in 1 hr 55 min.
Sift the flour into a bowl and create a well in the middle. Crumble the yeast into the well, add a tsp sugar and mix with a little milk and a little of the flour to form a pre-dough. Dust with flour, cover and leave to rise in a warm place for around 15 minutes.
Add the remaining sugar, the butter, salt, egg, vanilla sugar and the lemon zest and knead into a dough using an electric whisk with dough hooks. Add enough milk to prevent the dough from sticking.
Cover and leave to rise for around 30 minutes until it has doubled in size.
Roll out onto a floured work surface so the dough is approx. as thick as the back of a knife and cut in to 7 cm squares. Brush with water and fold into triangles. Cover with a tea towel and leave to rise for another 15 minutes.
Heat enough oil in a pan so that the beignets can 'swim' and cover a wire rack with greaseproof paper. Once the fat is hot enough (bubbles will appear on a wooden spoon held in the pan) fry the beignets until golden brown. Ensure that the fat is not too hot and that the beignets are evenly cooked on all sides.
Place on greaseproof paper to dry and dust with icing sugar while still hot.