Searing and stuffing a boneless thigh is one of the best ways to enjoy this cut. The key is to fold the thigh onto itself so its skin wraps entirely around the outside of the parcel. This way, you get a nice sear all around, while the meat inside—pressed together and insulated from direct, drying heat—stays tender. You can stuff the thigh with anything—from minced garlic and herbs to dried fruit—as long as your filling is fully cooked or quick-to-cook and won't burn easily if it spills out onto the hot pan. I prefer to eat dark meat warm, so I suggest serving these thighs as soon as I cook them. If you cannot find boneless thighs with skin, ask your butcher to remove the single bone from the meat—or do it yourself.
First, make the Refrigerator-Door Mustard: Finely chop the capers, peppercorns, and anchovy fillets by hand or in a food processor and combine well. Mix with both mustards. Store in the refrigerator for up to 1 month.
Season the skin side of the chicken with 1 teaspoon of the salt. Flip over and season the flesh side with the remaining salt. Let cure for 30 minutes before stuffing.
Preheat the oven to 400°F. Place 1 tablespoon of the mustard down the center of each thigh. Bring one side of the thigh over the other to enclose the filling. Stretch the skin so it covers all the meat and secure the seam with a toothpick.
Heat an ovenproof medium pan over medium-high heat for 30 seconds. Add the oil and tilt the pan to coat the surface. Add the thighs, seams facing to one side. Turn the heat down to medium; cook until the skin is deeply golden and crisp, 6 to 7 minutes. Turn to sear the other side, about 5 minutes more.
Once both sides are seared, carefully pour the excess fat out of the pan. Place the pan in the oven and roast until the chicken is fully cooked, 5 to 7 minutes. Place the thighs on a serving plate. Add the thyme and cold butter, if using, to the still-hot pan. Swirl to infuse the butter and combine it i with the other bits in the pan. As soon as the butter melts, spoon it liberally over the chicken. If you want, discard the thyme spring. Serve immediately.
*BONING A CHICKEN THIGH: Lay the thigh skin side down on your cutting board. With a thin, sharp knife, trace the full length of the bone to expose it fully. Next, scrape along one side of the bone, from joint to joint, to release the meat. If you focus on carefully cleaning the bone, rather than cutting at the meat, you’ll leave the chicken nicely intact. As you continue to scrape and loosen the bone from the meat—don’t forget to cut around the joints—you’ll be able to roll it over and cut it out.
Ronna Welsh is the owner of Purple Kale Kitchenworks, a New York cooking school. She has been teaching chefs and cooks strategies for cooking simply, efficiently, and creatively for more than two decades. Her paradigm-shifting ideas have been profiled in The New York Times, Wall Street Journal, Bon Appétit, and Tasting Table.