1. Heat oven to 400 degrees F.
2. With knife held horizontal to board, butterfly each breast by slicing through thickest part of breast lengthwise without cutting through; open like a book.
3. Lightly whisk together egg and milk in shallow dish. In another shallow dish, spread crumbs.
4. Place 3 dried tomato slices on each breast. Top with 1 slice cheese, folded in half. Sprinkle all breasts with thyme. Fold butterflied flap over cheese. Secure breasts with wooden pick.
5. Dip in egg mixture. Coat with crumbs. Place on rimmed baking sheet. Repeat with remaining breasts. Lightly coat with nonstick cooking spray.
6. Bake in 400 degree F oven 25 to 30 minutes; turn once. Makes 4 servings.