Preheat oven to 350 degrees F.
Wash and peel potatoes, and cut into 1-inch pieces.
Place in a large pot, and add enough cold water to cover by about 2 inches. Bring to a boil over medium-high heat, and reduce to a simmer.
Cook until tender and easily pierced with a paring knife, about 20 minutes.
Transfer to a colander to drain; return to pan, cover, and set aside.
Meanwhile, heat a large skillet over medium heat. Add bacon, and cook until crisp and browned, turning once. Transfer to paper towels to drain; let cool, and crumble into pieces.
Using a hand mixer, mash the potatoes in pan until light and fluffy.
Add the cream cheese, butter, and sour cream, and beat until combined and smooth. Add the green onions, 2 cups cheddar cheese, half the bacon, salt, and pepper. Stir until well combined.
Transfer to a 9 x 13 inch baking pan sprayed with nonstick cooking spray.
Top with remaining 1/2 cup cheddar cheese.
Bake until top is slightly golden and potatoes are heated through, about 30 minutes.
Remove from oven; garnish with remaining bacon.