Heat the oven. Preheat to 400°F (200°C).
Lightly grease a 9x13-inch baking dish or line with parchment for easy cleanup.
Prep the chicken. Pat the chicken dry with paper towels. If the breasts are thick, pound them to an even 3/4–1-inch thickness so they cook evenly.
Make the sauce. In a bowl, whisk together Dijon, whole grain or yellow mustard, honey, melted butter, garlic, vinegar or lemon juice, paprika, salt, and pepper until smooth.
Coat the chicken. Place the chicken in the baking dish. Spoon about two-thirds of the sauce over the top, turning the pieces to coat.
Reserve the rest for basting.
Bake. Bake uncovered for 15 minutes. Remove the dish, spoon the remaining sauce over the chicken, and return to the oven.
Finish cooking. Bake another 10–15 minutes, until the internal temperature reaches 165°F (74°C) in the thickest part. Total bake time is usually 25–30 minutes for breasts, 30–35 for thighs.
Rest and serve. Let the chicken rest 5 minutes so the juices settle.
Spoon the pan sauce over the top. Garnish with chopped parsley or thyme if you like.