Preheat oven to 400°F. Poke a few holes in each potato with a fork and place them on a baking sheet. Bake for 45 minutes or until potatoes are tender.
Cut potatoes in half lengthwise and scoop out the insides, leaving about 1/4-inch of the skin intact. Place the potato skins on the baking sheet.
In a medium mixing bowl, mash the potato insides with the butter, sour cream, Cheddar cheese, Parmesan cheese, green onions, garlic powder, salt and pepper. Mix until all ingredients are combined.
Spoon the potato mixture into each potato skin. Top with additional cheese, if desired.
Bake for an additional 15 minutes or until cheese is melted and potatoes are heated through.
Interesting Facts
Twice-baked potatoes are a great way to use up leftover mashed potatoes.
You can substitute the Cheddar and Parmesan cheese with any cheese of your choice.
You can also top the potatoes with cooked bacon or chives.