Roasted garlic, tangy buttermilk, and chicken stock pack a lot of flavor into these low-fat mashed potatoes. Prep and Cook Time: 1 1/4 hours. Notes: Chicken demi-glaceâ€”a deep brown, glazelike, intensely flavored reduction of chicken stockâ€”can be found at specialty markets. You can make your own by cooking 4 cups reduced-sodium chicken broth over medium-high heat until reduced to 1/2 cup. You can keep the demi-glace, covered and chilled, for up to 1 week, or frozen for up to 2 months.