Preheat your oven to 350 degrees F. Grease a casserole dish and set aside.

Place the potato chunks in a large pot, cover with water, and add 1 tbsp of kosher salt. Bring to a boil, then reduce heat to simmer until potatoes are tender (about 15-20 minutes).

While potatoes cook, heat a skillet over medium heat and cook the bacon until crispy. Drain on paper towels and set aside.

Drain the potatoes and return them to the pot. Add 2/3 cup of milk and the butter. Mash until smooth and creamy.

Stir in the sour cream, remaining milk, and 1 tsp of kosher salt into the mashed potatoes. Mix until well combined.

Fold in half of the mozzarella and cheddar cheese, along with the cooked bacon and green onions, reserving some bacon for topping.

Transfer the mashed potato mixture to the prepared casserole dish. Sprinkle the remaining cheeses and bacon on top.

Bake in the preheated oven for 20-25 minutes.

DEVOUR!