Chicken Breasts with Chipotle Beurre Blanc

4 boneless skinless chicken breast halves
1 Tbsp olive oil
7 Tbsp unsalted butter, cut up, softened, divided
1/4 C minced onion
1 large garlic clove, minced
1/4 C dry white wine
2 Tbsp balsamic vinegar
1 chipotle chile in adobo sauce, minced
1 Tbsp heavy whipping cream
1 tsp adobo sauce
1/4 tsp salt
1/4 tsp freshly ground pepper

Place chicken breasts between 2 pieces of parchment paper; pound to 1/4" thickness. Heat large skillet over medium-high heat until hot. Add oil and 1 Tbsp of the butter; cook until butter is melted. Add chicken; cook 5-6 minutes or until chicken is no longer pink in center and juices run clear, turning once. Place chicken on plate; cover loosely with foil to keep warm. Add onion and garlic to skillet. Cook 2 minutes or until softened. Add wine and vinegar. Cook until most of the liquid has evaporated. Reduce heat to medium. Whisk in remaining butter, 1 tablespoon at a time. Stir in chipotle chile, cream, adobo sauce, salt and pepper. Spoon sauce over chicken.