Preparation Cook all potatoes in large pot of boiling salted water until very tender, about 15 minutes. Drain. Return potatoes to pot. Meanwhile, melt butter with oil in small skillet over medium heat. Add garlic and sauté until golden, about 5 minutes. Add garlic mixture to potatoes and mash. Add 1/4 cup milk and stir until potato mixture is smooth, adding more milk by tablespoons if potatoes are dry. Season with salt and pepper.
Preparation Cook all potatoes in large pot of boiling salted water until very tender, about 15 minutes. Drain. Return potatoes to pot. Meanwhile, melt butter with oil in small skillet over medium heat. Add garlic and sauté until golden, about 5 minutes. Add garlic mixture to potatoes and mash. Add 1/4 cup milk and stir until potato mixture is smooth, adding more milk by tablespoons if potatoes are dry. Season with salt and pepper.