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 ½ cup cheddar cheese.
Bake until top is slightly golden and potatoes are heated through, about 30 minutes.
Remove from oven; garnish with remaining bacon.
Notes
Make-Ahead Tip: If you make this ahead of time be sure to refrigerate until baking.Feel free to add any other seasonings you like to the mashed potato mixtureStorage Notes: Either scoop the leftover mashed potatoes into an airtight container or leave them in the casserole dish and cover it with the lid or aluminum foil and store in the fridge for up to 5 days.