Wash the meat. Boil up l water in 3⁄4 and stir in broth. Cover and simmer for about 20 minutes.
Meanwhile peel and wash the carrots, cut them in half lengthwise and slice them. Add to the meat in the last 5-7 minutes and cook with it. Then take the meat out of the stock and put it aside. Pour stock through a sieve and collect.
Clean and possibly wash mushrooms. Heat butter in a pot. Fry the mushrooms for about 5 minutes. Season with salt and pepper. Dust with flour and briefly sauté lightly. Add stock while stirring, bring to the boil and simmer for about 3 minutes.
Preheat oven (electric cooker: 200 °C/circulating air: 175 °C/gas: see manufacturer). Cut meat into cubes. Add meat, carrots, frozen peas and cream to the sauce. Bring to the boil once and season to taste with salt, pepper and lemon juice.
Fill the fricassee into a wide ovenproof dish.
Finely grate the parmesan. Remove the rolls from the tin. Cut 4 rolls in half horizontally (use the remaining rolls for other purposes or bake them in the oven). Spread the roll halves on the fricassee.
Whisk the egg, spread on the rolls and sprinkle with parmesan. Bake in a hot oven for 15-20 minutes.