In a saucepan , heat the butter and sauté the onion and rosemary for 5 minutes, stirring occasionally.
Coat the meat with flour , throw in the pan, raise the heat to medium and brown evenly, turning occasionally.
Season , pour the milk and bring to a boil.
Lower the heat, cover the pan and simmer the meat for 30 minutes.
Add the fennel seeds, cover the pan again and cook for about 30 minutes.
Dissolve the cornstarch in 1 tablespoon water, toss in the pan and cook, stirring, until thickened.
Serve the rabbit on a platter with the sauce.