Mashed Potato Casserole

My mashed potato casserole recipe is loaded with rich goodness, including butter, sour cream, and cream cheese. Seasoned with garlic and thyme, this dish makes for a perfectly indulgent side – aka, the star of any holiday spread!

Cheesy mashed potato casserole recipe

Potatoes have a habit of stealing the show. Warm, comforting, and oh-so satisfying – spuds are one of my favorite ingredients to cook with. 

I especially love elevating the humble mashed potatoes, getting creative with Caramelized Onion Mashed Potatoes, Savory Mashed Sweet Potatoes, and even Mashed Cauliflower Potatoes.

Today, I’m bringing you a loaded mashed potato casserole, filled with creamy-dreamy ingredients and just a touch of thyme; the butter topping gives this casserole a gorgeous golden crust that makes it all the more inviting. 

Serve up a tray, and get ready to go back for seconds (and thirds…). 

Ingredients needed

Here’s a little bit on everything that goes into my loaded mashed potato casserole:

• Russet potatoes: The base of this casserole is, of course, potatoes! I like russet potatoes for their high starch content; this makes them really fluffy and smooth when mashed. This recipe calls for 4 lbs, peeled and cubed. 
• Salt: I use 1 tbsp of salt in the boiling water when cooking the potatoes. This helps infuse the potatoes with a bit of flavor. I use an additional tsp to season. 
• Cream cheese: To make this casserole extra creamy and indulgent, I add an 8-oz brick of softened cream cheese. This helps the potatoes mash like a dream!
• Butter: For even more creaminess, I add ½ cup softened butter (or 1 stick). I also use 2 tbsp, cubed into small chunks, as a topping while baking. This gives our casserole a browned crust on top. 
• Sour cream: 1 cup of sour cream adds a welcome acidity to this casserole. 
• Milk: I also use 1 cup of milk to keep the potatoes from drying out during their long baking time. 
• Garlic: 3 cloves of minced garlic add a delicious flavor to this dish, roasting beautifully in the oven. 
• Pepper: I use ½ tsp pepper for depth, cutting through the rich ingredients. 
• Thyme: Finally, I add 1 tsp thyme; this woodsy flavor keeps the casserole from tasting too heavy. For an extra special touch, fresh thyme is always welcome!

Kitchen tools required

To make this cheesy mashed potato casserole recipe, gather a few kitchen essentials:

• Dutch oven
• Cutting board + kitchen knife
• Peeler
• Potato masher
• 9×13 casserole dish

You’ll also need measuring cups, including 1 cup, ½ cup, 1 tbsp, 1 tsp, and ½ tsp. 

How to make mashed potato casserole

First up, preheat your oven to 375°F while you prepare the casserole. 

Add water to a large Dutch oven along with 1 tbsp salt. Bring the water to a boil, then add 4lb of peeled and cubed russet potatoes.

Boil until the potatoes are fork-tender and beginning to break apart, then drain. Add potatoes back to the pot. 

To your Dutch oven, add 8oz softened cream cheese, ½ cup butter, 1 cup sour cream, 1 cup milk, 3 cloves minced garlic, 1 tsp salt, ½ tsp pepper, and 1 tsp thyme. Mash well using a potato masher until most of the chunks are gone. 

Pour your potato mixture into a 9×13 casserole dish and add 2 tbsp of butter, cubed into small chunks, on top. 

Bake for 60 minutes, then let it set for at least 30 minutes before digging in!

Recipe tips

Below are some common mashed potato casserole questions. Don’t see the answer you’re looking for? Leave a comment at the bottom of this post!

How to serve my loaded mashed potato casserole

These mashed potatoes make a delicious side to any weekday or holiday spread. I recommend serving with a flavorful protein and veggie-focused side dishes. Here are a few of my favorite combinations:

• French Onion Chicken and Oven Roasted Honey Carrots
• Easy BBQ Baked Tempeh and Healthy Green Bean Casserole
• Baked Meatballs and Kale Superfood Salad
• Easy Spatchcock Chicken and Maple Balsamic Brussels Sprouts
• BBQ Turkey Meatloaf and Shaved Brussels Sprout Salad

Feel like eating a bowl of mashed potato casserole on its own? I’m not judging! In fact, I’m celebrating your choices. 

Optional toppings for mashed potato casserole

The best thing about this mashed potato recipe is that it’s super versatile, based on the spread you’re creating. Mix and match flavors with creative toppings, and make this recipe your own!

A few topping suggestions include:

• Shredded cheese, crumbled feta, or sprinkled parmesan 
• Crispy shallots
• Bacon bits
• Toasted breadcrumbs
• Fresh thyme or rosemary sprigs
• Chopped chives (add after baking)

Can I use a different type of potato? 

Absolutely. I like russet potatoes for their light and fluffy texture, though Yukon Golds would be a good alternative. They’ll produce an overall creamier casserole. 

How do I make this recipe plant-based? 

For a dairy-heavy recipe, it’s surprisingly easy to make this casserole vegan (thanks, modern grocery providers!). To make a plant-based potato casserole, simply follow these substitutions:

• Use a dairy-free cream cheese like Violife or Daiya. 
• Opt for vegan butter like Miyoko’s or Earth Balance.
• Choose a plant-based sour cream like Violife or Kite Hill. 
• Swap milk for your favorite dairy-free variety. Oat, almond, and soy would all work! Just make sure it’s unflavored and unsweetened. 

Storing leftovers

Allow leftovers to cool completely before transferring them to an airtight container. Store in the refrigerator for up to four days. 

To prepare this dish ahead of serving, follow the cooking instructions through step three, then refrigerate. Add cubed butter on the top right before baking!

How to reheat leftovers

When you’re ready to serve this casserole, preheat your oven to 350°F. Add a splash of milk or cubed butter to the dish, covering the top with tin foil to prevent it from drying out. 

Bake for 20-30 minutes, or until it’s hot. 

If you liked this recipe, you’ll want to try these!

Dig into these savory side dishes (seriously, you’re going to love them):

• Green Bean Almondine
• Best Classic Mac and Cheese Recipe
• Shaved Brussels Sprout Salad
• Cornbread Sausage Stuffing
• Garlic Parmesan Smashed Potatoes

Recipe by Erin Antoniak and Photos by Bake and Bacon