Preheat oven to 200°C (400°F).

Stir melted butter with sage, paprika, garlic powder, mustard powder, salt, and pepper. Rub this seasoned butter onto chicken thighs.

Place onions in an ovenproof dish measuring about 33 x 23 cm (13 x 9 in.) and pour on broth. Set chicken on onions. Bake for about 1 hour, or until meat easily comes off bone and internal temperature of chicken reaches 82°C (180°F). Serve chicken with onions and green beans.