Instructions

Adjust oven rack to middle position and heat oven to 200 degrees. Combine 2 teaspoons minced thyme, 1 teaspoon lemon zest, ½ teaspoon salt, and ¼ teaspoon pepper in bowl. Spread ½ cup all-purpose flour in shallow dish. Place 4 (6- to 8-ounce) boneless, skinless chicken breasts, trimmed, on cutting board and cover with plastic wrap. Using meat pounder, gently pound chicken to even thickness. Pat chicken dry with paper towels and sprinkle with thyme mixture. Working with 1 breast at a time, dredge in flour, shaking off excess.
Heat 2 tablespoons extra-virgin olive oil in 12-inch stainless-steel skillet over medium-high heat until just smoking. Cook chicken until well browned and registers 160 degrees, about 5 minutes per side. Transfer to plate and keep warm in oven.
Cook 2 ounces pancetta, cut into ¼-inch pieces, in remaining 2 tablespoons oil in now-empty skillet over medium heat until rendered and crisp, about 3 minutes. Add chopped stems from 1 pound Swiss chard and cook until softened, 3 to 5 minutes. Stir in 4 thinly sliced garlic cloves, ¼ teaspoon red pepper flakes, remaining ¼ teaspoon salt, and remaining ¼ teaspoon pepper and cook until fragrant, about 30 seconds. Stir in 1 (15-ounce) can cannellini beans and their liquid and any accumulated chicken juices, scraping up any browned bits, then stir in leaves from 1 pound Swiss chard, cut into 1-inch pieces. Cover and cook, stirring occasionally, until chard is tender, about 4 minutes. Slice chicken and serve with chard mixture, passing lemon wedges separately.