Then fry the goulash, onions and mushrooms in the oil. When the liquid is gone, deglaze with 500 ml beef stock (which is nice and spicy), lower the oven and simmer for about 45 minutes. Season to taste with salt, pepper, garlic and parsley.
Then thicken with a sauce thickener or flour. Then taste well. I still add milk or cream for the sauce, of course before thickening.