It couldn’t be easier.
The full recipe, with step-by-step photos, is further below.
How To Make Baked Mashed Potatoes Ahead
Prepare mashed potatoes through Step 5.

Credit:Caitlin Bensel; Food Stylist: Torie Cox
Let cool, then cover, and refrigerate the casserole for up to two days before serving.
To reheat, let potatoes stand at room temperature while the oven preheats, about 30 minutes.
Bake, covered with aluminum foil, 25 minutes.

Credit:Caitlin Bensel; Food Stylist: Torie Cox
Uncover and bake 25 to 30 minutes longer or until potatoes are heated through.
Spray a 2-quart baking dish with cooking spray.
Cook potatoes:
Place potatoes in a stockpot and add enough water to cover by 1 inch.

Credit:Caitlin Bensel; Food Stylist: Torie Cox
Stir in 1 tablespoon kosher salt.
Drain potatoes and return to pot.
Heat on HIGH in 30-second intervals until the butter has melted.

Credit:Caitlin Bensel; Food Stylist: Torie Cox
Mash potatoes:
Add butter mixture and cream cheese to potatoes.
Add cheese and seasonings:
Stir in 1 1/2 cups shredded cheese, remaining 1 tsp.
salt, pepper, and garlic powder into mashed potatoes.

Credit:Caitlin Bensel; Food Stylist: Torie Cox
Transfer to prepared baking dish.
Sprinkle with remaining shredded cheese.
Sprinkle with scallions or chives, if using.

Credit:Caitlin Bensel; Food Stylist: Torie Cox

Credit:Caitlin Bensel; Food Stylist: Torie Cox

Credit:Caitlin Bensel; Food Stylist: Torie Cox

Credit:Caitlin Bensel; Food Stylist: Torie Cox