Mix together the mozzarella and cheddar cheese in a bowl. Remove 1/4 cup of the mixture and set both bowls aside.
Bake potatoes in microwave until tender. Cut each potato in half lengthwise. Scoop out potatoes, leaving 1/8-inch shell.
Mix potato with sour cream and butter. Mash with potato masher. Stir in bacon (reserve a tablespoon or so for sprinkling on top) and 1 1/2 tablespoons chives. Add 1 1/4 cups of the shredded cheese mixture and mix well. Fill potato shells with mixture.
Sprinkle with remaining cheese and bacon.
Place on baking sheet. Bake at 350°F 25 minutes or until hot. Garnish with remaining chives.
Notes
Other tasty additions would include chopped onion, minced garlic, or a sprinkle of Parmesan cheese.
Remember to leave about an 1/8-inch potato inside the skin so that the shell doesn't collapse.