Remove all the rosemary leaves from the woody stems.
Chop the rosemary leaves with the garlic over a board, using a large knife.
Melt the butter in a small pot and
sprinkle all the sides of the meat with butter
press the meat over the board with chopped rosemary and garlic and cover all the sides
pour the remaining melted butter in a casserole with 2 tbsp of oil and heat
put the meat in the pot and let it golden all the sides
pour the milk in the pot and salt
cover with a lid and let it cook 40 minutes about (flipping 2 times)
Taste the milk if salted enough and remove the meat from the pot and keep it warm in aluminum foil
pour the tbsps of flour in the casserole and start whisking with a hand whip to be sure there are not lumps. After 3 minutes while is boiling it should be creamy, if necessary add 1 more tbsp of flour.
Cut the meat in slices of about 0,5 cm (not so thin) and place over a serving tray.
Pour the milk sauce over the meat
Serve immediately and eat