• If needed, adjust oven racks so that sheet pan sits in upper-middle of oven. Preheat oven to 425° Fahrenheit.

For the Vegetables

• Rinse 12 ounces chopped broccoli florets under running water and drain well. Pat florets dry with paper towels then add florets to large mixing bowl and set aside.
• Rinse 12 ounces peeled baby carrots under running water and drain well. Pat carrots dry with paper towels then add to large mixing bowl with broccoli. Set aside.
• Rinse 1 pound red potatoes under running water, scrubbing gently to remove all surface dirt. Once potatoes have been rinsed, dry potatoes well with paper towels, then place potatoes on cutting board. Cut potatoes into 1-inch cubes, then add potatoes to bowl with broccoli and carrots.
• Peel 1 medium red onion and discard papery skin. Slice onion in half, then chop each half into ½-inch long pieces. Add chopped red onion to bowl with broccoli, carrots, and potatoes.
• Add 2 tablespoons neutral-flavored oil, salt, and freshly cracked black pepper to bowl, then toss all ingredients together until vegetables are well-coated in oil and seasonings. Set bowl aside.
  

For the Chicken

• Place 2 ½ pounds bone-in, skin-on chicken thighs on cutting board. Pat each chicken thigh completely dry on all sides with paper towels.
• Season each chicken thigh generously with salt and freshly cracked black pepper, then flip chicken thighs over and repeat. Set cutting board aside.
  

For the One-Pan Chicken & Vegetables

• Transfer vegetables to sheet pan and spread vegetables out into single, even layer, covering entire pan.
• Place chicken thighs skin-side up on top of bed of vegetables. Arrange chicken thighs as needed to minimize overlap.
• Place ½ cup unsalted butter in microwave-safe bowl and place bowl in microwave. Microwave butter in 30-second bursts, stirring well after each burst, until butter is melted but not boiling. Carefully remove bowl of melted butter from microwave.
• Spoon approximately 1/3 of butter sauce over chicken thighs, covering each chicken thigh evenly. Reserve remaining butter sauce.
  
• Place sheet pan in preheated oven. Roast chicken thighs and vegetables 20 minutes.
• While chicken is roasting, add 6 cloves minced garlic, ½ teaspoon garlic powder, and 1 pinch salt to the remaining melted butter. Stir ingredients together until fully incorporated. Set aside.
• After 20 minutes, carefully remove sheet pan from oven and rotate. Spoon approximately half of the garlic butter sauce over chicken thighs, covering each piece evenly. Return sheet pan to oven and roast 20-25 minutes more.
  
• After 40-45 minutes total cooking time, insert internal meat thermometer into thickest area of chicken thighs to gauge doneness. Chicken should reach approximately 175° Fahrenheit. If needed, return sheet pan to oven and roast 5 minutes more, or until target internal temperature is reached. Be careful not to overcook vegetables.
  

To Serve

• After 5 minutes of rest time, remove aluminum foil and discard. Drizzle remaining garlic butter sauce over chicken thighs, then transfer chicken thighs to serving platter or plates.
• Season vegetables with additional salt and freshly cracked black pepper if desired, then toss vegetables in excess garlic butter sauce and pan juices.
• Once vegetables are well-coated, transfer. vegetables to serving platter or plates and serve immediately.