Clean oyster mushrooms and rub with kitchen paper. Wash and clean the mushrooms and chanterelles and possibly halve them. Wash chervil and chop, except for a few chervil leaves for garnishing. Wash, quarter and seed the tomatoes. Cut the flesh into small cubes.
Peel and finely chop the onion. Heat the fat. Sauté onion in it. Add mushrooms. Fry over high heat for about 5 minutes. Season with salt and pepper. Deglaze with stock, bring to the boil and stir in sauce thickener. Stir in chervil and tomatoes. For the omelette, beat the eggs and milk and season with salt. Heat oil in a pan.
Deglaze with stock, bring to the boil and stir in sauce thickener. Stir in chervil and tomatoes. For the omelette, beat the eggs and milk and season with salt. Heat oil in a pan. Add the egg milk. Fry for 2-3 minutes on each side. Put mushrooms on the omelette and serve garnished with tomato wedges and chervil leaves