Pound chicken breast thin with meat mallet or rolling pin. spread 1/2 cup spinach on each breast. Roll up and secure with toothpick. Heat oil in skillet, brown chicken breasts for aproximately 4 minutes. Add broth, mushrooms, onion and garlic, reduce heat and simmer until chicken is fully cooked. Remove chicken from pan. Mix cornstarch with aproximately 1/4 cup cold water, add to liquid remaining in pan, stir to thicken. Serve over chicken. This is excellent with some steamed brown rice. Serves 3.