Cut the roots off the oyster mushrooms. Separate into individual mushrooms, being careful not to break the caps. Put them in a bowl, cover with cold water and leave for 15 minutes. Drain in a colander, rinse with running water. Let dry.
In a small bowl, mix flour and 4 tbsp. l. starch. Add egg yolk and 200 ml cold water. Salt, mix thoroughly. You should get a dough of the consistency of liquid sour cream.
Heat vegetable oil strongly in a saucepan. Dip the oyster mushrooms first in the remaining starch, then in the batter. Fry in oil in small batches for 2 minutes.