Boil potatoes: Bring a large pot of water with 2 Tablespoons salt to a boil. Add 3 pounds peeled and chopped potatoes to the pot and boil for 15 minutes or until potatoes are tender.
Make mashed potatoes: Drain potatoes and place back in the pot. Add 1/4 cup milk (plus a little more, if needed), 5 Tablespoons melted butter, 1/2 cup sour cream, and some salt and pepper to taste. Mash with a potato masher (or you can use and electric mixer) until the butter is melted and the potatoes are creamy. Stir in 3/4 cup of the cheddar cheese.
Move potatoes to baking dish: Place the potatoes into 2 quart casserole dish coated with cooking spray. Add the remaining 1/2 cup of cheddar cheese on top.
Bake: Cover with foil and bake for 20 minutes. Remove the foil and add the 1/2 cup crumbled bacon to the top. Return to the oven and bake uncovered for another 20 minutes.
Add toppings and serve: Sprinkle chopped chives and parsley on top before serving.