Preheat oven to 400F. Scrub potatoes thoroughly with a brush; pat dry. Prick potatoes with a fork. Drizzle olive oil over each potato and sprinkle with salt. Wrap each potato in foil. Bake potatoes in the preheated oven about 1 hour or until tender. Remove and discard foil. Let potatoes stand about 15 minutes to cool slightly. Cut the potatoes in half lengthwise. Carefully scoop pulp out of each potato, leaving a 1/4- to 1/2-inch shell; set potato shells aside. Place potato pulp in a large bowl. Mash potato pulp with a potato masher or an electric mixer on low speed until nearly smooth.

In a 1- to 1-1/2-quart saucepan heat milk and butter over medium heat until butter is melted. Pour milk mixture over mashed potatoes; beat until smooth. Stir in sour cream, the 1 tablespoon snipped chives, and 2 tablespoons of the cheese. Season to taste with salt and pepper. Mound mixture into reserved potato shells. Sprinkle with remaining cheese. Place potatoes in a single layer in a 2-quart square baking dish.

Bake, uncovered, in a 400F oven about 20 minutes or until golden brown and heated through. If desired, garnish with snipped chives. Makes 4 servings.

Make-ahead directions: Prepare as directed through Step 2. Place potatoes in a single layer in an airtight container. Cover and chill for up to 24 hours. Before serving, preheat oven to 325F. Place potatoes in a 2-quart square baking dish. Bake, covered, in the preheated oven for 30 minutes. Uncover and bake about 15 minutes more or until potatoes are golden brown and heated through.

Bacon-Cheddar Twice-Baked Potatoes: Prepare as above, except in Step 2 stir in 1/3 cup cooked, crumbled bacon along with the sour cream; substitute cheddar cheese for the Gruyere cheese.

Southwestern Twice Baked Potatoes: Prepare as above, except in Step 2 substitute snipped fresh cilantro for the chives; substitute Monterey Jack cheese with jalapenos for the Gruyere. Serve with purchased salsa. Omit optional chive garnish.