A tasty twist on simple mashed potatoes - the sweet potato and zesty yogourt give this dish the upper hand on your festive holiday table. Ingredients 4 unpeeled garlic cloves ½ teaspoon extra-virgin olive oil 2 medium sweet potatoes (about 1 pound total) 2 medium russet potatoes (about 1 pound total) 1 tablespoon unsalted butter 2 tablespoons coarsely chopped fresh flat-leaf parsley, plus for garnish 1 tablespoon finely chopped fresh sage 1¾ teaspoons coarse salt Pinch of freshly ground pepper ½ cup plain yogurt or sour cream Method: Preheat oven to 400ºF, with racks in centre and lower thirds. Put garlic on a piece of aluminum foil; drizzle with oil. Fold to form a packet. Place garlic packet and the potatoes on centre rack; with a baking sheet on lower rack to catch any drips. Bake, until the potatoes are very tender when pierced with the tip of a knife, about 60 minutes. Remove from oven and let cool slightly, about 5 minutes. Skin the potatoes and pass through a ricer into a medium bowl. Squeeze garlic from skins into bowl with potatoes. Stir in butter, parsley, sage, salt, and pepper. Stir in yogurt, and serve.