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A close up of Garlic Parmesan Mashed Potato Casserole, shown in a purple baking dish with a serving spoon
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5 from 7 votes

Garlic Parmesan Mashed Potato Casserole Recipe

Garlic Parmesan Mashed Potato Casserole recipe makes the PERFECT Thanksgiving and holiday side dish! Creamy russet potatoes are cooked with garlic cloves, then mashed with butter, milk and Parmesan cheese. Top with additional Parmesan before baking to create a crispy exterior on this comforting casserole. No matter if you're serving the family for a holiday or on a weeknight, Mashed Potato Casserole packs a flavorful punch for any meal!
Prep Time15 mins
Cook Time1 hr
Total Time1 hr 15 mins
Course: Side Dish
Cuisine: American
Servings: 8 large servings
Calories: 292kcal
Author: Julie Evink


  • 3 lbs. russet potatoes , scrubbed, peeled and diced into 1” cubes
  • 5 garlic cloves , whole
  • 1 teaspoon kosher salt (to season put in water for the diced potatoes)
  • 4 tablespoons unsalted butter
  • 1 cup whole milk
  • 1 3/4 cups parmesan cheese , shredded and divided
  • 1 teaspoon black pepper , freshly ground
  • 1.2 teaspoon kosher salt


  • Using a sharp knife, chop the scrubbed and peeled potatoes into 1” cubes.
  • Fill a large saucepan or Dutch oven with water, then add the potatoes to the water. Place the garlic cloves in the water, as well.
  • Season the water with a teaspoon of salt.
  • On the stovetop, heat the water and potatoes over high heat and bring to a boil. Cook until the potatoes are fork tender, about 20 minutes.
  • Drain the potatoes, and place back in the saucepan.
  • Measure out the butter, milk and 1 cup of parmesan cheese on top of the potatoes.
  • Using a hand mixer on a low speed, slowly blend the ingredients together until smooth and creamy.
  • Season the potatoes with salt and pepper.
  • Preheat the oven to 350°F. Spray a 9'' x 13'' baking dish with nonstick cooking spray, and set aside.
  • Transfer the mashed potatoes into the prepared baking dish. Sprinkle the additional ¾ cup cheese on top of the casserole.
  • When the oven is preheated, transfer the casserole to the oven.
  • Bake for 25 minutes, then turn up the heat to 425°F. Bake for an additional 15 minutes, or until the cheese has browned.
  • Remove from the oven, and let cool slightly.
  • Serve warm, and enjoy!


Make Ahead Tip: Make the mashed potatoes a day or two before the big day, and transfer them into a baking dish. (You won’t cover them in cheese or bake now—that’ll come the day of!) All you’ll do now is cover them with plastic wrap, then store in the fridge.
The day of, unwrap the casserole dish, top with cheese and bake until the cheese is golden, brown, bubbly and delicious.


Serving: 1serving | Calories: 292kcal | Carbohydrates: 33g | Protein: 12g | Fat: 12g | Saturated Fat: 7g | Cholesterol: 32mg | Sodium: 1012mg | Potassium: 777mg | Fiber: 2g | Sugar: 2g | Vitamin A: 395IU | Vitamin C: 10.3mg | Calcium: 321mg | Iron: 1.7mg