Preheat the oven to 350 degrees. Coat a large baking dish with butter.
Cook the bacon bits in a large skillet over medium heat until crisp and the fat has been rendered. Drain on paper towels until needed.
Peel and cut the potatoes into 1-inch chunks. Place them, along with a sprinkling of salt, into a large saucepan and add enough water to cover the potatoes by 1-inch.
Bring the water to a boil over high heat then reduce the heat to medium-low and simmer until the potatoes are very fork-tender, about 15-18 minutes. Drain the potatoes.
Place the butter into the milk and heat it in the microwave for 45 seconds or until the butter is melted.
Pour the milk mixture onto the potatoes along with the sour cream; season with sea salt and freshly cracked pepper, to taste. Beat the potatoes using a hand mixer until really creamy and smooth.
Place into the prepared baking dish and smooth the top with a spoon.
Sprinkle the shredded cheese on top then bake for 15-20 minutes or until the cheese is melted and the potatoes are warmed through.
Sprinkle the top with crisp bacon bits and green onions. Serve immediately. Enjoy.