Preheat oven to 350°F.
Spread the sliced onions and half of the garlic cloves in the bottom of a 9×13 casserole dish.
Pour the bone broth and wine over the onions and garlic. Place chicken pieces skin-side up on top of the onions.
In a small bowl, combine the butter, salt, pepper, and rosemary. Use a pastry brush to paint the butter mixture on the chicken pieces. Pour any remaining into the casserole pan.
Scatter the remaining garlic around the chicken in the pan.
Bake chicken for 40-45 minutes, until the thickest part of the thickest piece registers at 165°F on a meat thermometer.
If the skin isn’t browned enough for your taste, set the pan under the broiler for 3-4 minutes.
Serve roasted garlic chicken warm with mashed potatoes and your favorite green vegetable for a complete and filling meal!