Spray a rimmed baking sheet with cooking spray and preheat oven to 400 degrees. Trim chicken if necessary, then pat dry with a paper towel. Add mustard to a small shallow bowl, then mix Parmesan, tarragon, garlic powder, and pepper in a separate shallow bowl.
Dip chicken in mustard and lightly coat both sides (shaking off excess), then dredge chicken in the seasoned Parmesan and arrange the thighs in a single layer toward one end of your prepared baking sheet.
Wash, trim, and halve green beans, then place them in a large bowl and toss with olive oil, garlic, sea salt, and pepper. Spread green beans out on the other half of the baking sheet, then sprinkle them evenly with Parmesan.
Bake at 400 degrees for 20 minutes, then serve!
* If you don't have or don't enjoy tarragon, you can substitute oregano + a little basil.
Sheet Pan Parmesan Chicken Thighs & Green Beans from Mashup Mom: https://www.mashupmom.com/sheet-pan-parmesan-chicken-thighs-green-beans/