Description

This rich and creamy Russet Mashed Potato Casserole combines fluffy russet potatoes with cream cheese, sour cream, and garlic, baked to golden perfection with a buttery top. Ideal for holiday dinners, potlucks, or any comforting side dish, it’s make-ahead friendly and packed with deep flavor from fresh thyme and bay leaf infusion.

Ingredients

Scale

For cooking the potatoes:

3 lb russet potatoes (waxy variety works best for creaminess)
1 tbsp kosher salt
4 thyme sprigs (fresh preferred for better aroma)
1 bay leaf
6 garlic cloves (unpeeled, for subtle flavor)

For the casserole:

2 tbsp unsalted butter (for topping)
Kosher salt to taste
8 oz cream cheese (softened to room temperature)
3/4 cup whole milk (warm, helps incorporate smoothly)
Black pepper to taste (freshly ground preferred)
1 cup sour cream (full-fat for creamier texture)
6 tbsp unsalted butter (I use Kerrygold for richness)

Instructions

Prepare the Potatoes and Aromatics: Peel and cut the russet potatoes into evenly-sized chunks about 2 inches each to ensure uniform cooking. Place the potatoes in a large pot and cover with cold water by about 2 inches. Add 1 tablespoon kosher salt, unpeeled garlic cloves, bay leaf, and fresh thyme sprigs. Bring to a boil over high heat, then reduce to a simmer and cook for approximately 20 minutes until potatoes are fork-tender.
Drain and Prepare for Mashing: Drain potatoes and garlic in a colander and let sit for 3 minutes to evaporate excess moisture, which is essential for a creamy texture. Remove and discard bay leaf and thyme sprigs. Peel the softened garlic cloves and set aside. Resting the potatoes helps mash more smoothly without overworking.
Create the Creamy Potato Base: Transfer warm potatoes and peeled garlic to a large bowl and mash with a potato ricer or masher, leaving some chunks for texture. Warm milk slightly in a separate container to help it incorporate smoothly. Add softened cream cheese, 6 tablespoons unsalted butter, sour cream, and gradually pour in the warm milk while gently stirring until creamy. Season with kosher salt and freshly ground black pepper to taste.
Assemble the Casserole for Chilling: Butter a 9×13 inch baking dish and transfer the creamy potato mixture into it, smoothing the top evenly. Dot the surface with 2 tablespoons unsalted butter cut into small pieces. Allow to cool to room temperature, then cover tightly with plastic wrap or foil and refrigerate overnight or up to 2 days to enhance flavor and allow proper setting.
Bake and Serve: Preheat oven to 350°F about 15 minutes before baking. Remove casserole from fridge, uncover, and bake for about 1 hour until the top is golden brown and edges bubble slightly. Let rest for 5 minutes before serving to help the casserole hold its shape and enhance texture.

Notes

Always bring dairy ingredients like cream cheese, butter, sour cream, and milk to room temperature or warm slightly before mixing to avoid gluey texture.
Use a potato ricer or food mill for fluffiest texture and avoid overworking potatoes to prevent stickiness.
Cut potatoes into evenly sized chunks for even cooking and avoid undercooked or mushy pieces.
Bake at 350°F to heat casserole thoroughly without drying or toughening the edges.
This casserole can be made ahead and refrigerated for up to 2 days or frozen up to 2 months for convenience.
Reheat covered in a 350°F oven for 20–30 minutes or microwave individual portions, adding a splash of milk if dry.

Prep Time: 35 minutes
Cook Time: 1 hour 5 minutes
Category: Side Dish
Method: Baking
Cuisine: American

Keywords: mashed potato casserole, russet potatoes, creamy mashed potatoes, holiday side dish, make-ahead casserole, comfort food, potluck recipes