Braised Chicken with Swiss Chard, Tomatoes, and Balsamic Vinegar Over Polenta

Braised Chicken with Swiss Chard, Tomatoes, and Balsamic Vinegar Over Polenta
Adapted from Cooks Illustrated

Ingredients
8 bone-in, chicken breasts (about 3 pounds), trimmed of excess fat and skin
1 tablespoon olive oil
1 large onion , halved and sliced about 1/4 inch thick (about 2 cups)
1 tablespoon tomato paste
3 cloves garlic , minced or pressed through garlic press (about 1 tablespoon)
1 can (14 1/2 ounces) diced tomatoes , drained
2 cups low-sodium chicken broth
1/4 cup dry white wine
1/4 teaspoon red pepper flakes
1 1/2 tablespoons chopped fresh thyme leaves
1 bay leaf
12 ounces Swiss chard , washed and dried
1/2 cup balsamic vinegar

Instructions
1.Adjust oven rack to lower-middle position; heat oven to 350 degrees. Sprinkle both sides of chicken thighs with salt and pepper. Heat oil in nonreactive Dutch oven over medium-high heat until shimmering but not smoking; add chicken thighs skin-side down and cook without moving them until skin is crisped and well browned, 10 to 12 minutes. Using tongs, turn chicken pieces and brown on second side, about 5 minutes longer; transfer thighs to large plate.

2. Pour off all but 1 teaspoon fat from pot. Add onion and tomato paste and cook over medium heat, stirring occasionally and scraping bottom of pot with wooden spoon, until tomato paste begins to darken, about 4 minutes (if bottom of pot becomes very dark and sticky, stir in 1 to 2 tablespoons water). Add garlic and cook, stirring constantly, until fragrant, about 1 minute. Stir in tomatoes, chicken broth, and wine, scraping up browned bits with wooden spoon. Add red pepper flakes, thyme, and bay. Remove and discard skin from chicken thighs, then submerge chicken bone-side up in liquid, adding any chicken juices accumulated on plate. Increase heat to high, bring to simmer, cover, then place pot in oven. Cook until chicken offers no resistance when poked with tip of paring knife but meat still clings to bone, 40 to 55 minutes.

3. While chicken cooks, trim stems from Swiss chard (Cut stems crosswise into 1/4-inch pieces; halve leaves lengthwise, then cut crosswise into 1/4-inch-thick strips. Set stems and leaves aside separately. Also while chicken cooks, simmer balsamic vinegar in 8-inch nonreactive skillet over medium-high heat until thick, syrupy, and reduced to 1/4 cup, 3 to 5 minutes (begin measuring volume when vinegar begins to cling to sides of saucepan). Set vinegar reduction aside.

4. Using slotted spoon, transfer chicken to plate and tent with foil; discard bay leaf. Bring liquid in Dutch oven to simmer over medium-high heat; add chard stems and cook, stirring occasionally, until almost tender, about 8 minutes. Add chard greens and cook until wilted, about 2 minutes. Stir about 1/3 cup sauce into balsamic reduction to loosen, then stir mixture into sauce; adjust seasoning with salt and pepper. Return chicken and accumulated juices to sauce, cook until heated through, about 2 minutes, turning chicken once or twice. Use slotted spoon to transfer chard to serving dish or individual bowls; place chicken thighs on chard, then spoon sauce over. Serve immediately over polenta.