Peel and finely chop the onion. Pluck sage leaves from the stems, wash and chop 3 leaves finely. Peel garlic and press it through a garlic press. Heat the fat. Fry onions, garlic and chopped sage in it.
Sweat flour in it. Add cream and milk while stirring and bring to the boil. Season to taste with salt, pepper and lemon juice. Wash the meat, dab dry and tap flatter. Cover with 1 slice of ham and the remaining sage leaves.
Overfold the meat and pin it with wooden sticks. Season with salt and pepper. Fry in hot oil for about 2 minutes on each side and remove. Pour sauce into the frying fat, bring to the boil again briefly and season to taste.
Serve the meat and sauce garnished with lemon.