Clean and slice the mushrooms, wash the chicory and cut into wide pieces. Halve the feta cheese and wrap it in a kitchen towel and let it dry a little. Warning: the cheese is very salty and you have to decide how much of it you want to use.
Pour the oil into the pan and fry the mushrooms for about 4 - 5 minutes. Stir every now and then and season with salt and pepper. Then add the onions and fry again for 3 - 4 minutes. Add the chicory, sauté briefly and stir.
Heat about 2 tablespoons of oil in another pan and add the cheese. Mix the thyme, oregano and pepper and sprinkle on the cheese. Turn the cheese over and sprinkle with the spice mixture again.
Fry the cheese for about 5 minutes (it becomes very soft and runs a little, but this is normal). Turn the cheese over and over until it is browned on both sides. Serve with the mushroom pan.