Preheat the oven to 475°. In a large enameled cast-iron casserole, melt 1 tablespoon of the butter in the oil over moderately high heat. Season the chicken inside and out with salt and pepper, add the rosemary to the cavity and tie the legs together. Set the chicken in the casserole on 1 breast. Cover and roast in the oven for 30 minutes. Carefully turn the chicken onto its other breast, cover and roast for 20 minutes. Turn the bird on its back and add the garlic and shallots. Cover and roast for 20 minutes longer, or until the juices run clear when a thigh is pierced. Transfer the chicken to a platter, cover and keep warm.
Skim the fat from the juices in the casserole. Add the wine and boil, stirring, until the sauce is reduced by half, about 5 minutes. Pour in any collected chicken juices. Add the cream and boil until the sauce is thick enough to coat a wooden spoon, about 5 more minutes. Swirl in the remaining 1 tablespoon butter until blended and season with salt and pepper. Pour the sauce into a sauceboat; serve with the chicken.
Roasted fingerling potatoes or the smallest white new potatoes you can find.
Pair with a lightly oaked California Chardonnay, like Gundlach-Bundshu.