Preheat the oven to 425F. Line a baking sheet with parchment paper.
Mix ingredients for the Honey Dijon Sauce together in a small bowl and set aside.
Add the sliced poatoes, onion and chicken thighs to a medium bowl. Add a little over half the Honey Dijon Sauce to the bowl and mix to coat everything.
Lay the carrots on the baking tray and drizzle the remaining honey mustard sauce over the carrots, using your hands to spread the sauce to coat.
Add the chicken, potatoes and onion to the tray and spread everything out evenly. If you don't have a large enough baking tray for everything to fit well, I'd reccomend using two.
Bake for 15 minutes, remove from the oven and flip the carrots and stir around the potatoes and onion. Return to the oven and bake for another 15-20 minutes until the chicken is cooked through (internal temp of 165F), and the potatoes and carrots are fork tender. Enjoy!