Place milk, sour cream and butter out to come to room temperature.
Scrub russet potatoes under water. Dry off potatoes with a towel. Place potatoes onto a parchment lined baking sheet. Rub each potato with a drizzle of cooking oil. Sprinkle with salt. Poke 8 holes all over potatoes. Bake in 425 degree oven for 45 minutes. Pull out of oven and allow to rest until cool enough to easily handle. While potatoes are cooking prepare bacon. (you can either fry up bacon in a pan or bake in the oven for 15-20 minutes until crisp. Place bacon on a paper towel lined plate to allow grease to drain. Crumble up bacon once crisp and cooled.
Turn oven down to 350 degrees. Lightly grease a 9 x 13 baking dish.
Using a spoon pull out the cooked potato from the skins and place into a large bowl. If you want to add some skin to the bowl just leave it on 2 of the potatoes for a more rustic look.
Mash up potatoes in large bowl until you reach desired texture. I like to leave mine chunky. Add 1/3 of the crumbled bacon, sour cream, milk, butter, salt, pepper and 1 cup of cheese. Mix all ingredients in the bowl until well combined. Taste for any extra seasoning if needed.
Pour potato mixture into casserole dish evenly. Sprinkle 1 cup of cheese and the rest of bacon across casserole. Place in 350 degree preheated oven uncovered for 20-25 minutes until cheese is nicely melted and casserole is heated through.
Take out of oven, garnish with sliced green onions or fresh parsley. Enjoy.