In a small bowl whisk together mustards, maple syrup, apple cider vinegar and garlic. After you get a smooth consistency add pepper to taste (I used probably 1/2 a teaspoon, you don’t need a lot here).
Arrange the chicken skin side up in a casserole pan (I needed to use two to fit them all) and pour 2/3 of the marinade over the chicken. Toss to fully coat the thighs.
Roast chicken for about 50 minutes, after 35 minutes brush on the remaining marinade.