Wash the potatoes and boil in water for about 20 minutes. Clean, wash and slice the mushrooms. Peel and finely dice onion
Quench and peel the potatoes. While still hot, press them through a potato ricer and let them cool down a little. Knead with egg yolk, 40 g flour and semolina, season. Form dough into a roll on a little flour and cut into 1-2 cm thick slices. Press in with a fork, so that grooves are formed
Heat the fat. Sauté onion and mushrooms in it. Deglaze with broth and cream, bring to the boil. Wash basil, chop finely if necessary. Thicken sauce with sauce thickener. Season with basil, salt and pepper
Cook the gnocchi in portions in plenty of boiling salt water for 4-6 minutes. The gnocchi are cooked when they rise to the surface. Drain well and serve with sauce and parmesan