Technical Stages :

• Prepare the butter seasoning :
• In a shallow dish, mix the soft butter, chopped parsley, salt, pepper (to taste), lemon juice and lemon rind. Mix with a fork.
• Put the meat in a large bowl, along with the egg. Season.
• Mix to homogeneize the preparation. Form 4 small round balls, level them (without pressing too much) to a thickness of about 4 cm (1,57 inches).
• Trim the slices of white bread and cut them so that they have the exact dimensions of the meat. Cook the hamburgers in oil over strong heat, 2 minutes on each side (rare). Lower the heat and cook for an additional 2 minutes (done).
• Meanwhile, put the bread in a toaster. Spread the butter mix on it, put a burger steak on top and on each piece of meat spread the remaining 1/4 of the butter.