Preheat oven to 350 degrees. Place chicken breasts in double gallon sized zippered bags. With a mallet on the smooth side, pound the chicken 1/4" thick. Place the pounded chicken breasts on a baking sheet. Sprinkle both sides with salt and pepper. Spread an even amount of Boursin cheese over all four chicken breasts. Evenly distribute mozzarella cheese on top of the Boursin. Carefully roll up chicken, seam side down. Wrap each chicken roll with a slice of prosciutto, tucking the ends under the chicken roll. Melt butter and olive oil together in baking dish or glass pie plate. Place chicken rolls in baking dish. Bake for about 30 minutes or until internal temperature is 165 degrees. With a pastry brush, baste the chicken rolls several times during the cooking process with the butter/olive oil mixture. (This will give the chicken rolls added flavor and a beautiful glossy finish.) Serve with pasta, rice, vegetables or a salad. Serves 4.