Donuts with custard.Fluffy donuts, homemade recipe.

Donuts with custard. Fluffy donuts, homemade recipe.
Ingredients:
Dough:
Dry yeast – 11 gr.
Milk or water – 1 tbsp. (250 gr.)
Egg – 1 pc.
Sugar – 2 tbsp
Vegetable oil – 2 tbsp. l.
Flour – about 500 gr.
A pinch of salt

Filling:
Egg – 1 pc.
Milk – 1 tbsp.
Sugar – 0.5 tbsp.
Flour – 1-5 tbsp.
Butter – 50 g.
Vanillin