Heat oven to 350°F; pat chicken dry with paper towels.
Mix flour, salt, pepper, garlic powder, and thyme in a shallow dish; dredge chicken in mixture.
Heat oil in a large oven-safe skillet or Dutch oven over medium-high. Sear chicken skin-side down 4-5 minutes until golden brown, then flip and sear 3-4 minutes more. Remove and set aside.
Cook onions in same skillet 5 minutes until softened; add broth and butter, scraping up browned bits.
Return chicken; cover and bake 75-90 minutes until tender and cooked through.
Transfer chicken to a platter. Over medium stovetop heat, stir cream into skillet; simmer 3-4 minutes until slightly thickened.
Pour gravy over chicken; garnish with parsley and serve with mashed potatoes or biscuits.