Step 1: Heat the Oven and Choose the Dish - Preheat your oven to 400°F. Give it time to reach the full temperature before the chicken goes in, since a properly heated oven helps the outside start browning right away. Choose a casserole dish that holds all eight thighs in a single layer with a little room between them. A crowded dish traps more steam, while a little space helps those edges turn golden. You do not need to grease the dish because the chicken and olive oil will provide enough moisture.
Step 2: Add the Chicken and Dry Seasonings - Place the boneless skinless chicken thighs in a large mixing bowl. Sprinkle in the paprika, onion powder, garlic powder, and black pepper. I like to scatter the spices across the whole bowl instead of dropping them in one pile, because that gives you a head start on even seasoning. Use clean hands or sturdy tongs to turn the chicken several times until the dry mixture reaches every fold and surface.
Step 3: Build the Dijon Herb Coating - Add the Dijon mustard, dried thyme, salt, olive oil, and brown sugar to the seasoned chicken. Toss again until every thigh looks glossy and evenly coated, with no dry pockets of spice hiding at the bottom of the bowl. Take an extra thirty seconds here. A thorough coating means the tangy mustard, warm spices, and gentle sweetness bake directly onto the meat instead of ending up in one concentrated spot. The mixture should cling to the chicken rather than run off like a thin marinade.
Step 4: Arrange the Chicken for Even Roasting - Transfer the coated thighs to your casserole dish and arrange them in a single layer. Smooth each piece open instead of leaving it folded under itself, which helps the chicken cook evenly from edge to center. Scrape any seasoning mixture left in the bowl over the top. When I am trying to get dinner moving quickly, this is the moment I wash the mixing bowl and set out the side dishes, because the rest of the recipe needs very little attention.
Step 5: Bake Until Juicy and Nearly Done - Place the casserole dish in the oven and bake for 30 minutes. The chicken will release flavorful juices as it cooks, and the surface will slowly change from glossy red brown to a deeper roasted color. At the 30 minute mark, check the thickest piece with an instant read thermometer. You are looking for at least 165°F in the center. If the thighs are especially thick, they may need the additional five minutes listed in the recipe.
Step 6: Spoon the Juices and Finish Browning - About five minutes before the chicken is finished, carefully slide the dish forward and spoon some of the hot pan juices over each thigh. This small step keeps the surface moist and carries all that paprika, garlic, mustard, and thyme back over the meat. Return the dish to the oven for about five minutes, or until the tops look deeply golden and lightly caramelized. If you want more color, give the chicken a few additional minutes while watching it closely so the brown sugar does not scorch.
Step 7: Rest, Garnish, and Bring It to the Table - Remove the casserole dish from the oven and let the chicken rest for five minutes. I know everyone is usually circling the kitchen by this point, but resting gives the juices time to settle back into the meat instead of running onto the cutting board. Spoon a little more of the pan liquid over the thighs, scatter chopped cilantro on top, and serve while everything is warm. The fresh green garnish wakes up the rich roasted flavors and makes the whole dish look ready for company.