How to make
Cut the meat and put it into a saucepan, add cold water and bring to a boil. Add the chopped onions, leeks, carrots and peppers. Bring it to a boil again, reduce the heat and cook until the meat is a bit more tender.
Remove the cooked meat. Melt the butter and fry the flour. Add the broth from the cooking and boil the sauce.
Add the mushrooms and cook for another 15 minutes. Beat the milk with the egg yolk and cream and add half of it to the mixture above.
Once you have a smooth mixture, add the rest of the milk. Do not allow the sauce to over boil. Serve the meat drizzled with the mushroom sauce.