Chicken with Tomato-Balsamic Pan Sauce

Remove and reserve chicken tenders (if attached) for another use. Slice each breast in half horizontally to make 4 pieces total. Place on a cutting board and cover with a large piece of plastic wrap. Pound with the smooth side of a meat mallet or a heavy saucepan to an even thickness of about 1/4 inch. Sprinkle with 1/4 teaspoon each salt and pepper. Place flour in a shallow dish and dredge the cutlets to coat both sides, shaking off excess. (Discard remaining flour.)

Heat 2 tablespoons oil in a large skillet over medium-high heat. Add 2 pieces of chicken and cook, turning once, until evenly browned and cooked through, 2 to 3 minutes per side. Transfer to a large serving plate and tent with foil to keep warm. Repeat with the remaining chicken.

Add the remaining 1 tablespoon oil, tomatoes and shallot to the pan. Cook, stirring occasionally, until softened, 1 to 2 minutes. Add vinegar; bring to a boil. Cook, scraping up any browned bits from the bottom of the pan, until the vinegar is reduced by about half, about 45 seconds. Add broth, garlic, fennel seeds and the remaining 1/4 teaspoon salt and pepper. Cook, stirring, until the sauce is reduced by about half, 4 to 7 minutes. Remove from heat; stir in butter. Serve the sauce over the chicken.