Heat butter and cook onions and garlic for 10 minutes. Add minced lamb and cook, stirring, until browned. Sprinkle flour on top of meat and stir well, allowing flour to cook. Add tomatoes, bay leaf and parsley and cook for 20 minutes, stirring occasionally. Feel free to add a little water as it cooks, if necessary, to create more of a sauce. Taste for salt and pepper and adjust accordingly.