Preheat oven to 450 degrees.
In a small bowl, whisk together the Dijon mustard, Maple syrup, vinegar, red pepper flakes, salt, and pepper. Set aside.
Line a 9x13 casserole dish with two layers of foil (or some super heavy duty foil). The foil helps with cooking and helps the maple syrup not burn on your pan. Make sure not to poke any holes in the foil, or you will lose all the yummy sauce while cooking.
Spread the chicken thighs out in the pan on top of the foil.
Pour the sauce over the chicken.
Cook uncovered in the oven at 450 degrees for 40 minutes. Meanwhile, have your rice and veggies cooking as well.
Serve and Enjoy!