For the beer chicken, divide the chicken into pieces and fry all around in hot butter. Finely chop the onion, cut the smoked bacon into small cubes, add to the pieces of meat and stir in the tomato ketchup.
Deglaze with a small amount of pilsner, simmer and keep adding beer. When the chicken pieces are cooked, remove from the pan and keep warm.
For the beer chicken, add finely sliced mushrooms to the pan. Whisk the whipping cream and egg and add to the sauce (do not boil!). Season with salt, cayenne pepper and parsley and pour over the chicken pieces.