Pour off all but 2 tablespoons of fat from the skillet. Add the shallots and cook over moderate heat, stirring, until softened, 2 minutes. Add the brandy and cook until most of the liquid has evaporated. Add the stock and cook, scraping up any browned bits, until slightly reduced, 3 minutes. Stir in the heavy cream and simmer until slightly thickened, 1 minute. Remove from the heat and stir in the remaining 2 tablespoons of butter. Season the sauce with salt.