Dinner

Russet Mashed Potato Casserole Recipe

ByLana Polati January 9, 2026January 9, 2026

Introduction

This Russet Mashed Potato Casserole is a creamy, rich side dish made with fluffy russet potatoes, cream cheese, sour cream, and garlic. Baked with a buttery topping, it’s perfect for potlucks, holidays, or cozy family dinners. Easy to prepare ahead and loved by all, it turns classic mashed potatoes into something special.

A white baking dish filled with a layered shepherd's pie or cottage pie, showing a top layer of golden-brown mashed potatoes with lightly toasted peaks and crests, sprinkled with black pepper. The mashed potato layer is thick, creamy, and textured with swirls from a spoon or spatula. Below the mashed potatoes, a hint of the filling is slightly visible, suggesting a rich and hearty meat and vegetable mix inside. The dish sits on a wooden surface with a white marbled texture background, and a silver spoon is placed nearby, slightly out of focus. Photo taken with an iphone --ar 4:5 --v 7

Ingredients

3 lb russet potatoes
1 tbsp kosher salt
4 fresh thyme sprigs
1 bay leaf
6 garlic cloves (unpeeled)
8 oz cream cheese (softened to room temperature)
3/4 cup whole milk (warmed)
1 cup sour cream (full-fat)
6 tbsp unsalted butter (softened)
2 tbsp unsalted butter (for topping)
Kosher salt to taste
Freshly ground black pepper to taste

Instructions

Step 1: Peel and cut the russet potatoes into evenly sized 2-inch chunks. Place them in a large pot and cover with cold water by about 2 inches. Add 1 tablespoon kosher salt, unpeeled garlic cloves, bay leaf, and thyme sprigs.
Step 2: Bring the water to a boil over high heat. Reduce to a simmer and cook for about 20 minutes until potatoes are fork-tender.
Step 3: Drain the potatoes in a colander and let sit for 3 minutes to evaporate excess moisture. Remove and discard bay leaf and thyme sprigs. Peel the softened garlic cloves and set aside.
Step 4: Transfer warm potatoes and garlic to a large bowl. Mash using a potato masher or ricer until slightly chunky.
Step 5: Warm the milk slightly. Add cream cheese, 6 tablespoons butter, sour cream, and warmed milk to the potatoes. Stir gently until creamy and combined.
Step 6: Season with kosher salt and freshly ground black pepper to taste.
Step 7: Butter a 9×13 inch baking dish. Transfer the mashed potato mixture and smooth the top. Dot with 2 tablespoons butter cut into small pieces.
Step 8: Allow to cool to room temperature, then cover with plastic wrap or foil and refrigerate overnight or up to 2 days.
Step 9: Preheat oven to 350°F about 15 minutes before baking. Remove the casserole uncovered and bake for about 1 hour until golden on top and edges bubble.
Step 10: Let rest 5 minutes before serving to help it set and hold shape.

Tips & Variations

Use Yukon Gold potatoes for a creamier, buttery flavor but a less fluffy texture.
If you don’t have cream cheese, substitute with extra sour cream for a slightly less rich casserole.
Swap sour cream with full-fat Greek yogurt or crème fraîche for a different tang.
Bring dairy ingredients like cream cheese, butter, sour cream, and milk to room temperature to avoid gluey potatoes.
Avoid over-mixing potatoes; mash just until combined for light, fluffy texture.
Use fresh thyme sprigs for aroma but dried thyme (1 tsp) works if added to the cooking water.
Try adding roasted garlic instead of raw for a milder, deeper flavor.

Storage

Store leftovers tightly covered in the refrigerator for up to 4 days. The flavors improve with time. To freeze, wrap tightly in plastic and foil, and freeze for up to 2 months. Thaw overnight in the fridge. Reheat covered in a 350°F oven for 20–30 minutes or microwave individual portions for 2–3 minutes, stirring halfway and adding a splash of milk if needed.

How to Serve

The image shows a white rectangular casserole dish filled with a baked mashed potato topping that is golden brown and slightly crispy on the top layer. The mashed potato layer is thick, creamy, and unevenly swirled with some spots more browned than others. The casserole dish sits on a white marbled surface with a soft gray cloth and a shiny silver spoon to the side. In the blurry background, there are out-of-focus white and brown salt and pepper shakers and a white ceramic pitcher. The overall look is warm and inviting, with the creamy potato topping clearly the main focus. Photo taken with an iphone --ar 4:5 --v 7

Serve this delicious recipe with your favorite sides.

FAQs

Can I use other types of potatoes for this casserole?

Russet potatoes are preferred for their starchy, fluffy texture that absorbs butter and cream well. Yukon Golds are a good alternative for a creamier taste but will be less fluffy. Avoid red or waxy potatoes, as they tend to be gummy and watery.

Can I make this casserole ahead of time?

Yes, this casserole is ideal for making ahead. Prepare and chill it covered in the refrigerator for up to 2 days. Baking it directly from the fridge allows the flavors to deepen and the dish to hold together nicely.