For the filling, peel and finely dice the onion. Thoroughly clean, wash and possibly chop the mushrooms. Heat 1-2 tablespoons of oil in a frying pan. Fry the onion and mushrooms. Season with salt and pepper.
Let it cool down.
Peel approx. 16 cloves of garlic individually from the tuber and place unpeeled on a lightly oiled baking tray. Bake in the preheated oven (electric cooker: 200 °C/circulating air: 175 °C/gas: level 3) for about 20 minutes.
Knead 250 g flour, 1/2 teaspoon salt, 1 egg, 7-8 tablespoons oil and 3-4 tablespoons cold water first with the dough hooks of the hand mixer, then work into a firm dough with your hands. Roll out thinly on a lightly floured work surface.
Cut out about 28 circles (8 cm Ø).
Whisk the egg whites. Brush the edges of the dough with egg white all around. Place the mushroom mixture on the circles, fold down to form a semicircle and press the seams together firmly with your fingers. Spread the corners with egg white and press them together.
Pelmenis in portions in plenty of boiling salt water. Let it simmer at low heat for 12-15 minutes. Lift out and drain well.
Squeeze the garlic out of its skin and crush it slightly with a fork. Wash the sage and remove the leaves. Heat half the butter in a frying pan. Sauté half the garlic and half the sage in it. Fry half of the pelmenis.
Prepare the rest of the pelmenis in the same way. Grate or slice the cheese. Arrange pelmenis with it. Drink tip: Vodka, e.g. Sareema.