Place a large rimmed baking sheet in the oven and preheat the oven to 450 degrees with the pan in the oven. Preheating the baking sheet helpd ingredients cook envenly.
While the oven preheats, place broccoli florets and onion in a medium bowl. Drizzle with 1 tablespoon of oil. Sprinkle with salt and pepper and toss to coat. Set aside.
Make the rub: In a small bowl, combine the brown sugar, cumin, chili powder, paprika, onion powder, garlic poowder, salt, black pepper, and chipotle powder.
Rub the chicken thighs with the remiaining 1 teaspoon of the oil. Sprinkle all over with seasoning rub.
When the oven is preheated, use an oven mitt to carefully remove the hot sheet pan from the oven. Spray the sheet pan with cooking spray. Spread the vegetables in an even layer on the baking sheet leaving spaces for the chicken thighs. Nestle the chicken thighs among the vegetables.
Return the baking sheet to the oven and bake for 15 minutes. Stir the vegetables and continue cooking until the chicken is cooked through and registers 165 degrees about 5 minutes more.
While chicken is cooking, prepare the honey mustrard sauce by combining all of the ingredients.
Serve honey nustard sauce with chicken and vegetables. Any leftover sauce may be served in an airtight container in the refrigerator for up to 4 days.