1. Season both sides of chicken breasts with salt and pepper. Place flour on sheet of waxed paper. Dip chicken in flour to coat both sides; shake off any excess flour and place chicken on another piece of waxed paper.
2. Heat oven to 375 degrees F.
3. Heat 1 tablespoon oil and 1 tablespoon butter in a large nonstick skillet over medium-high heat.
4. Add 6 chicken breasts to skillet; saute until lightly browned, about 3 minutes per side. Place chicken in 15-1/2 x 10-1/2 x 1-inch baking pan in single layer. Repeat with remaining oil, butter and chicken.
5. Bake chicken in 375 degree F oven for 20 minutes or until no longer pink in center.
6. Meanwhile, add garlic and prosciutto to skillet; cook over medium heat, stirring constantly, for 3 minutes. Add wine and rosemary; cook, stirring up any browned bits from bottom of skillet, for 2 minutes.
7. Add tomatoes and broth. Bring to boiling. Reduce heat; simmer 10 minutes.
8. Place chicken on serving platter; pour sauce over top. Serve immediately. Makes 12 servings.