Chicken, Mushroom, and Potato Stew

Finely chop 1 small yellow onion. Trim the dark green parts from 1 large or 2 small leeks and discard or save for another use. Halve the white and light green parts lengthwise and rinse in between the layers to remove grit. Cut crosswise into 1/4-inch half-moons.

Pat 1 1/2 pounds boneless, skinless chicken thighs dry with paper towels. Season all over with 1 teaspoon of the kosher salt and 1/4 teaspoon black pepper. Heat 1 tablespoon of the olive oil in a Dutch oven or large pot over medium-high heat until shimmering. Working in batches, add chicken thighs in a single layer, taking care not to crowd the pot. Cook until the bottoms are golden-brown, 4 to 5 minutes. Flip and cook until the second side is browned, 2 to 3 minutes more. Transfer to a plate (the chicken will not be cooked through). Sear the remaining chicken, adding more oil to the pan as needed. Meanwhile, quarter 8 ounces cremini mushrooms (about 2 1/2 cups).

Reduce the heat to medium. Add the remaining 2 tablespoons olive oil and 1 tablespoon of the unsalted butter. Add the mushrooms and cook, stirring occasionally, until lightly browned, 7 to 8 minutes. Add the remaining 1 tablespoon unsalted butter, onion, and leeks. Season with the remaining 1 teaspoon kosher salt. As the vegetables start to release liquid, scrape up the browned bits from the bottom of the pot and cook until liquid has evaporated and the bottom of the pot begins to brown again, 8 to 10 minutes. Meanwhile, pick the leaves from 2 to 4 large sprigs fresh thyme until you have 1 teaspoon. Cut the chicken into large bite-sized (about 1 1/4-inch) pieces.

Sprinkle 1 tablespoon all-purpose flour over the vegetables and stir and cook until well-coated, about 1 minute. Add 1/4 cup dry white wine and cook, scraping up any browned bits from the bottom of the pot, until thickened, about 1 minute. Return the chicken and any accumulated juices to the pot. Add the thyme, 1 (32-ounce) carton low-sodium chicken broth, and 1 bay leaf. Bring to a boil over high heat.

Reduce the heat as needed and simmer uncovered for 10 minutes. Meanwhile, halve 1 pound Yukon gold potatoes lengthwise, then cut crosswise into 1/3-inch-thick half-moons.

Add the potatoes and simmer, stirring occasionally, until potatoes the potatoes are cooked through and the chicken is tender, about 20 minutes. Meanwhile, strip the leaves from the stems of 1 small bunch Swiss chard. Halve the leaves lengthwise, stack them, and cut crosswise into 1-inch pieces (about 4 cups). Discard the stems or save for another use.

During the last few minutes of simmering, add the Swiss chard and stir until wilted. Remove the pot from the heat and discard the bay leaf. Add 1/2 cup frozen peas, 1 tablespoon fresh lemon juice, and 1 tablespoon whole-grain mustard, and stir to combine. Taste and season with more kosher salt, black pepper, and/or lemon juice as needed.