1Heat oven to 350°F. Spray 11x7-inch baking dish with cooking spray. In 12-inch skillet, cook bacon over medium-high heat, stirring frequently, until crisp. Reduce heat to low; add onion and garlic; cook 2 to 3 minutes, stirring occasionally, until soft. Remove from heat; stir in bread crumbs. Stir in cheese, rosemary and egg; mix well.
2Unfold chicken thighs so inside faces up. Spoon stuffing over thighs, about 2 tablespoons each. Fold over, and secure with toothpicks. In same skillet, heat olive oil and butter. Cook thighs in skillet 2 minutes per side, until brown. Place in baking dish. In medium bowl, mix diced tomatoes and tomato paste. Pour over chicken.
3Cover with foil. Bake 1 hour to 1 hour 15 minutes or until thermometer inserted in center of chicken stuffing reads 165°F. Serve over cooked spaghetti if desired.