Substitutions

• Russet potatoes: Russets can replace Yukon Gold potatoes, though their softer, starchier texture may make the casserole slightly fluffier.
• Monterey Jack cheese: Monterey Jack can replace the Swiss cheese when you want a milder flavor that still melts smoothly.
• Mozzarella cheese: Low moisture mozzarella can replace the sharp cheddar for a gentler cheese flavor and a stretchier texture.
• Half and half: Use half and half instead of heavy cream for a lighter sauce, though the finished casserole may be a little less rich.
• Cream of onion soup: Condensed cream of onion soup works when condensed French onion soup is not available.
• Regular cheddar cheese: Mild or medium cheddar can replace sharp cheddar when cooking for children who prefer a softer cheese flavor.

Variations

• Bacon French onion potato casserole: Stir 8 slices of cooked and crumbled bacon into the cheese sauce before building the layers.
• Ham and potato casserole: Add 2 cups of diced cooked ham between the potato layers to turn the side dish into a hearty main meal.
• Steakhouse potato casserole: Add 8 ounces of sautéed mushrooms between the layers and finish the baked casserole with plenty of chopped parsley.
• Loaded French onion potato casserole: Top each serving with crumbled bacon, sliced green onions, and a small spoonful of sour cream.
• French onion chicken potato casserole: Layer 2 cups of cooked shredded chicken with the potatoes for a comforting complete dinner.
• Herb and onion potato casserole: Add chopped thyme or rosemary to the cream sauce for an earthy flavor that pairs especially well with roast beef.

Tips and Tricks

• Slice the potatoes evenly: Potatoes with a consistent thickness cook at the same pace and give the casserole a soft, uniform texture.
• Shred the cheese yourself: Freshly shredded cheese usually melts more smoothly because it does not contain the same coating used to keep packaged shreds separate.
• Cover the dish tightly: A snug layer of foil traps the steam needed to soften the potatoes during the first part of baking.
• Test the center potatoes: The center takes the longest to cook, so check there rather than testing only the soft slices near the edge.
• Allow extra time for thicker slices: Potatoes thicker than ⅛ inch may need another 10 to 15 minutes of covered baking before you add the final cheese.
• Rest the finished casserole: A 15 minute rest helps the sauce thicken, making the casserole creamier and much easier to serve.
• Watch the onion topping: Crispy fried onions can darken quickly, so add them during the last few minutes instead of at the beginning.
• Place the dish on a sheet pan: If your baking dish is very full, setting it on a rimmed pan will catch any sauce that bubbles over.

Serving Ideas

• Roast turkey: The creamy potatoes and savory onion sauce fit naturally beside turkey, gravy, stuffing, and green beans.
• Glazed ham: Salty, slightly sweet ham balances the rich cheese and deep onion flavor in the casserole.
• Roast chicken: A simple roast chicken and a green vegetable turn this potato casserole into a cozy Sunday dinner.
• Beef tenderloin: The Gruyère and French onion flavors make the casserole a strong partner for a special beef dinner.
• Pork chops: Serve it with pan seared or baked pork chops and steamed broccoli for a filling family meal.
• Green salad: A crisp salad with a bright vinaigrette helps balance the richness of the cream and cheese.
• Roasted vegetables: Brussels sprouts, asparagus, carrots, and green beans all bring color and freshness to the plate.

Storage and Make Ahead Tips

• Refrigerating leftovers: Cover the baking dish or transfer leftovers to an airtight container and refrigerate for up to 4 days.
• Reheating in the oven: Cover the casserole and warm it in a 325°F oven until hot throughout, adding a few fresh fried onions near the end if you want more crunch.
• Reheating individual servings: Microwave single portions in short intervals until heated through, pausing to check the center so the edges do not overcook.
• Assembling ahead: Build the casserole up to 24 hours before baking, cover it tightly, and keep it refrigerated.
• Freezing before baking: Assemble the casserole without the fried onion topping, wrap it securely, and freeze for up to 2 months.
• Thawing a frozen casserole: Move it to the refrigerator the night before you plan to bake it, then add extra covered baking time if the center is still very cold.
• Refreshing the topping: Leftover fried onions soften in the refrigerator, so add a small handful of fresh onions during reheating for renewed crunch.