Balsamic Chicken with Mushrooms

4 skinless, boneless chicken breasts
salt and pepper to taste
4 oz crimini mushrooms, sliced
1 small onion, chopped
olive oil
6 cloves garlic, minced
1/4 cup balsamic vinegar
3/4 cup chicken broth
1/4 teaspoon dried thyme
1 tablespoon butter

1. Pound chicken to 1/4 thickness and season with salt and pepper
2. Heat oil in a skillet over medium high heat and saute onion and garlic
3. Add chicken and brown on one side
4. Add mushrooms and turn chicken over and brown
5. Add vinegar, chicken broth, and thyme. Cover tightly and simmer over medium low heat for 5 minutes, turning mushrooms occasionally.
6. Remove chicken and place on a serving plate
7. Continue to simmer the sauce, uncovered, over medium high heat for about 7 minutes. Add in butter and pour mushroom sauce over chicken
8. Serve with rice or over a bed of spinach and quinoa, topped with cherry tomatoes and mozzarella cheese