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Supreme Mashed Potato Casserole

Supreme Mashed Potato Casserole

Our Supreme Mashed Potato Casserole is truly amazing! It starts with sour cream, butter and cheese. Add fantastic ingredients like, bacon, crispy fried onions, Ranch dressing and more and you end up with a truly magnificent potato casserole!
Course Side Dish
Cuisine American
Keyword baked potato, best side dish, casserole, easy side dish, mashed potato


  • saucepan
  • casserole dish (8-10 inches long by 6-8 inches wide or equivalent)


  • 8-10 russet potatoes
  • 2 tablespoons butter
  • cup milk
  • ½ cup sour cream or sour cream based flavored dip
  • 2 ¾ cups cheddar and monterey jack cheeses, shredded, divided
  • 1 teaspoon garlic salt
  • ½ teaspoon pepper


  • 2 tablespoons ranch seasoning (or ¼ cup ranch dressing and only ¼ cup of milk)
  • chives or green onions
  • ¼ cup parmesan cheese (optional)
  • bacon or bacon bits
  • green chiles, diced
  • crispy fried onions


  • Preheat your oven to 400 degrees.
  • Peel and chop potatoes, then boil in salted water until soft, about 15-20 minutes. Drain and return to pot or a large bowl.
  • Ideally, using a handheld mixer, add butter to your potatoes. I add butter first while the potatoes are hot so the butter melts easily.
    Supreme Mashed Potato Casserole
  • Add milk, sour cream, ranch (if using), cheese, garlic salt, pepper and any other option you want to include. Blend ingredients together. TASTE your potatoes and add more of whatever you think they need, if anything at all.
    Supreme Mashed Potato Casserole
  • Spray a casserole dish with cooking spray and press your potatoes into it. Try and make the top as even as possible.
  • First, I sprinkle bacon all over the top (if using), then crispy fried onions, and parmesan cheese (if using). Last, I sprinkle between ½ - 1 cup of shredded cheddar and monterey jack cheeses all over the top. Sometimes a little more, sometimes a little less.
    Supreme Mashed Potato Casserole
  • Bake for 25-30 minutes until top is a golden brown. Sometimes I will broil for a minute or two to darken the cheese a little more, if needed.
    Supreme Mashed Potato Casserole
  • Top with chives or green onions. Serve as desired.
    Supreme Mashed Potato Casserole