Roast Chicken and Chicken Gravy

whole chicken

Salt and freshly ground black pepper

garlic cloves, (smashed)

medium yellow onion, (peeled and sliced into halves (so you'll use 2 quarters))

Fresh poultry herbs, (see notes)

butter, (well softened)

Vegetable oil for skillet

Pan drippings remaining after roasting chicken

low-sodium chicken broth, divided

cornstarch

heavy cream ((optional))