Stuffed Mushroom-Cheese Potatoes

Preheat oven to 375 degrees. Bake potatoes until tender, about 45 to 60 minutes. Melt 1 tbsp. butter in a large skillet. Add mushrooms and cook until tender, stirring frequently, about 7 minutes. Add onions and cook 1 minute. Cut each potato in half lengthwise and scoop out insides leaving an 1/8 inch shell. Transfer potato insides to a large bowl and add cream cheese, sour cream, salt, pepper and 4 tbsp. butter and mash well. Stir in mushrooms and 1/2 cup cheddar. Mound mixture back into potato skins and sprinkle each potato half with 1 tbsp. cheddar. Place potatoes on a baking sheet and bake about 25 minutes until cheese is melted and potatoes are heated through.