Rinse rabbit, pat dry and cut into 8 serving pieces. Heat olive oil and butter in a roasting pan and brown meat on all sides. Peel onions and garlic. Remove meat from the pan and saute onions and garlic for a few minutes in the same pan, season meat with salt and pepper and add to the pan.
Add broth, cream, rosemary and bay leaf and cook, covered, in preheated oven at 220°C (approximately 425°F) for about 20 minutes. Reduce oven temperature to 180°C (approximately 350°F) and cook for 25 minutes more, basting meat with cooking juices often. Remove from the oven and serve.