Preheat oven to 400 degrees, and spray foil-lined baking sheet with cooking spray
Combine maple syrup and mustard in medium bowl, and mix well. Add roasted garlic, smash into mixture, and combine fully. Set aside.
Scrub baby potatoes. Cut potatoes in half or quarters, depending on size. The key is for all potatoes to be the same size. Toss potatoes in large bowl with onions. Drizzle with oil, and season with salt, pepper, onion powder and garlic powder.
Trim all excess skin from chicken. Keep only the skin on the top surface area. Lay chicken in shallow plate, and season both sides with salt and pepper.
Lay chicken skin side up on one side of baking sheet, and spoon half of the glaze mixture over the chicken thighs
Add 2 tablespoons of mixture to potato and onion mixture, and toss with hands to fully coat. Spread potatoes and onions out on other side of baking sheet
Put baking sheet in oven on lower rack, and roast for 25-30 minutes, until chicken is cooked to internal temperature of 165. Remove from oven, toss potatoes and onions, and spoon remaining glaze over chicken. Move sheet to top rack, and broil for about 10 minutes, checking once about halfway through to make sure the glaze doesn't burn.