Mix 2/5 cup (100 g) of flour with the salt in a large bowl. To it, add the yolks beaten with the beer and 1 tablespoon of oil. Beat until smooth, cover with a lid and put it in the refrigerator for 1 hour.
Then beat the egg whites into snow and carefully mix them with the crumbing. Dip the cut and shaped onion rings in milk. Then roll them in 1 1/3 tbsp (20 g) of flour, mixed with breadcrumbs and put them into the bowl of crumbing.
Fry these onion rings in preheated oil, drain on a cooking grid and serve while still warm.