Creamy Mashed Potato Casserole with Cheesy Breadcrumbs
A rich, comforting mashed potato casserole layered with tangy sour cream, sharp cheddar, and Dijon mustard, topped with buttered breadcrumbs and fresh parsley. The potatoes are boiled until tender, then riced and folded with warm milk and seasonings for a silky texture. This make-ahead dish is ideal for holiday dinners, potlucks, or family gatherings where you need a side that can sit in the fridge for up to two days before baking. The crispy, golden breadcrumb topping adds textural contrast to the creamy base, while cayenne pepper provides subtle heat. Perfect for feeding a crowd.
Ingredients
- 4 slices good quality white bread with crust, cut into quarters
- 2 tablespoons melted butter, for breadcrumbs
- ¼ cup fresh parsley, minced
- salt, to taste
- freshly ground black pepper, to taste
- 8 ounces extra-sharp cheddar cheese, shreddedgruyere or aged white cheddar1:1none
adds nuttier flavor
- 5 pounds russet potatoes, peeled and sliced into 3/4 inch rounds, rinsed
- 2 ½ cups whole milk, warmed
- 1 cup sour cream
- 8 tablespoons unsalted butter, melted
- 2 ½ teaspoons Dijon mustard
- 2 teaspoons garlic, minced
- ⅛ teaspoon cayenne pepper
Instructions
- 1
Heat oven to 300 degrees F.
- 2
Pulse bread in food processor until coarse crumbs form, about 6 pulses.
- 3
Toss breadcrumbs with melted butter, spread on rimmed baking sheet, and bake for about 20 minutes, stirring occasionally.
- 4
Cool breadcrumbs, then toss with parsley, salt, and pepper. Set aside with shredded cheese.
- 5
Place potato slices in large saucepan and cover with water.
- 6
Bring to boil, reduce to simmer, and cook until tender, about 15 minutes.
- 7
Drain potatoes thoroughly.
- 8
Pass potatoes through food mill or ricer back into saucepan.
- 9
Add warm milk, sour cream, melted butter, mustard, garlic, and cayenne to potatoes.
- 10
Stir until combined and season with salt and pepper to taste.
- 11
Spread potato mixture into 9 by 13 inch casserole dish.
- 12
Sprinkle with shredded cheddar cheese, then breadcrumb mixture.
- 13
Cover with plastic wrap and refrigerate up to 2 days, or proceed to baking.
- 14
Remove plastic wrap and cover dish with foil.
- 15
Heat oven to 350 degrees F.
- 16
Bake covered for 20 minutes.
- 17
Remove foil and bake 20 to 40 minutes more until heated through, checking with instant-read thermometer for doneness.
Tips
Use a food mill or ricer rather than a blender or mixer to avoid overworking the potatoes, which can make them gluey and dense.
Make this casserole up to 2 days ahead and refrigerate; bake from cold, adding 10-15 minutes to baking time.
Test doneness with an instant-read thermometer inserted into the center; it should read 165 degrees F when heated through.
Good to Know
Cover and refrigerate up to 2 days before baking. After baking, store covered in refrigerator up to 3 days. Do not freeze; texture becomes grainy when thawed.
Assemble entirely, cover with plastic wrap, and refrigerate up to 2 days. Bake directly from cold, adding 10-15 minutes to baking time.
Serve hot as a side dish alongside roasted meats, poultry, or at holiday and potluck dinners.
Common Mistakes
Do not use a blender or electric mixer on the potatoes to avoid overdeveloping gluten and creating a gluey texture.
Do not skip the food mill or ricer step; hand-mashed potatoes will be lumpy and inconsistent.
Do not remove foil too early; this allows the top to brown while the interior finishes cooking.
Substitutions
Vegan Options
for dairy-free version
General Alternatives
adds nuttier flavor
FAQ
Can I make this without a food mill or ricer?
Yes, but results will be less smooth. Use a potato masher and work gently, or pass potatoes through a sieve. Avoid blenders and electric mixers, which will make potatoes gluey.
What if my casserole isn't heated through after 40 minutes?
Continue baking in 5-10 minute increments, checking with an instant-read thermometer. Baking time varies based on dish depth and oven calibration. Center should reach 165 degrees F.
Can I freeze this casserole?
Not recommended. Freezing and thawing breaks down the creamy potato texture and causes graininess. Make and store in refrigerator up to 2 days, or bake and refrigerate up to 3 days.