French Onion Potato Bake Recipe

I’m sharing my French Onion Potato Bake, a potatoes and onions recipe where thinly sliced potatoes meet slowly caramelized yellow onions and minimal staples to reveal an unexpected twist worth reading about.

I never thought a simple bake could act like a small revelation, but this French Onion Potato Bake did. Thinly sliced yellow onions turn sweet and deep, and melting Gruyere cheese gives it that flaky, savory finish I cant stop chasing.

Calling it a Potato Onion Casserole makes it sound humble, but really it hides layers of flavor that make people ask what you did different tonight. I like that it looks fancy but wont make you sweat, and somehow always disappears faster than I planned.

Try not to tell everyone how easy it was, but you probably will.

Ingredients

• Yellow onions: Sweet when caramelized, adds fiber and depth, mostly carbs and antioxidants
• Potatoes: Starchy comfort, good potassium and fiber, mainly carbs, makes dish hearty
• Gruyere cheese: Melty nutty flavor, adds protein and fat, salty, browns beautifully on top
• Parmesan cheese: Intense umami, low moisture, salty kick, adds depth without too much creaminess
• Heavy cream: Makes it rich and silky, lots of fat and calories, little protein
• Butter: Adds richness and browning, full of saturated fat, classic French touch
• Thyme: Herby, slightly minty and lemony, lifts savory flavors with subtle brightness
• Beef or vegetable broth: Adds savory depth and umami, reduces salt need, boosts overall flavor

Ingredient Quantities

• 2 large yellow onions thinly sliced
• 2 tablespoons unsalted butter
• 1 tablespoon olive oil
• 1 teaspoon granulated sugar
• 1 clove garlic
• 1 teaspoon fresh thyme leaves or 1/4 teaspoon dried thyme
• 1 teaspoon Worcestershire sauce
• 1/2 cup beef or vegetable broth
• 2 pounds potatoes Yukon Gold or Russet peeled and thinly sliced
• 1 teaspoon kosher salt
• 1/2 teaspoon black pepper
• 2 cups grated Gruyere cheese about 8 ounces
• 1/2 cup grated Parmesan cheese about 50 g
• 1 1/2 cups heavy cream
• 1/2 cup whole milk
• 1 tablespoon butter
• 1/2 cup French fried onions or panko breadcrumbs optional
• 2 tablespoons chopped fresh parsley optional

How to Make this

1. Preheat oven to 375 F. Start the caramelized onions: heat 2 tablespoons unsalted butter and 1 tablespoon olive oil in a large skillet over medium heat, add the 2 large thinly sliced yellow onions, 1 teaspoon granulated sugar and a pinch of salt, cook stirring often until they’re soft and turning deep brown, about 20 to 30 minutes total.

2. Near the end of the onion time add 1 clove garlic minced and 1 teaspoon fresh thyme leaves (or 1/4 teaspoon dried), stir a minute, then pour in 1 teaspoon Worcestershire sauce and 1/2 cup beef or vegetable broth to deglaze; simmer until most of the liquid is reduced. Set onions aside.

3. While onions cook peel and thinly slice 2 pounds potatoes (Yukon Gold or Russet) about 1/8 inch thick, try to keep slices even so they cook the same. Toss the slices with 1 teaspoon kosher salt and 1/2 teaspoon black pepper and pat them dry with a towel if they feel wet.

4. Make the cheesy cream: warm 1 1/2 cups heavy cream and 1/2 cup whole milk in a saucepan over low heat with 1 tablespoon butter, don’t boil just warm. Stir in about 1 1/2 cups grated Gruyere and 1/4 cup grated Parmesan until melted; reserve about 1/2 cup Gruyere and 1/4 cup Parmesan for the top.

5. Butter a 9 by 13 inch or similar baking dish with a little of that reserved butter or oil. Arrange a single overlapping layer of potato slices across the bottom, spoon on some caramelized onions, then drizzle some of the cream-cheese mixture and sprinkle a little of the cheese. Repeat layers until potatoes, onions and cream are used, finishing with the cream in the dish.

6. Cover tightly with foil and bake at 375 F for 40 to 50 minutes, test with a knife in the center; potatoes should be tender.

7. Remove foil, sprinkle the remaining 1/2 cup Gruyere and 1/4 cup Parmesan on top and optionally scatter 1/2 cup French fried onions or panko breadcrumbs for extra crunch. Return to oven uncovered and bake another 15 to 20 minutes until bubbly and golden, or broil 1 to 2 minutes if you want a faster browning but watch it closely so it doesnt burn.

8. Let the bake rest about 10 minutes so the sauce sets a bit, then sprinkle 2 tablespoons chopped fresh parsley if using, slice and serve warm.

Equipment Needed

1. Oven set to 375 F, obviously you’ll need it preheated
2. Large heavy skillet, nonstick or stainless, for caramelizing the onions
3. 9 by 13 inch baking dish or similar, buttered before layering
4. Mandoline or a very sharp chef knife and cutting board for thin potato slices
5. Saucepan to warm the cream and melt the cheeses
6. Box grater or microplane for Gruyere and Parmesan
7. Measuring cups and teaspoons for cream, milk and seasonings
8. Wooden spoon or heatproof spatula for stirring and deglazing
9. Aluminum foil and a clean kitchen towel for covering and patting potatoes dry

FAQ

French Onion Potato Bake Recipe Substitutions and Variations

• Gruyere cheese: swap for Swiss or Emmental, or use sharp white cheddar if you want a stronger, tangier flavor; all melt well so the bake still gets gooey.
• Heavy cream: use 3/4 cup whole milk plus 1/4 cup melted butter for each cup of cream, or use half and half or canned evaporated milk in a pinch.
• Beef or vegetable broth: use low sodium chicken broth, mushroom stock for extra umami, or splash in a dry white wine instead of part of the liquid.
• French fried onions or panko: substitute plain breadcrumbs, crushed cornflakes, or extra grated Parmesan mixed with a little melted butter for a crispy topping.

Pro Tips

1. Slice the potatoes as even as you can. If you got a mandoline use it. Rinse the slices in cold water to wash off excess starch, dry them well, and they will stack and cook way more evenly.

2. Don’t rush the onions. Cook them low and slow until theyre deep brown, stirring often so they dont stick. If you want to speed things a bit a tiny pinch of baking soda helps browning, but use very little or it can give a soapy taste.

3. Warm your cream before adding the cheese and grate the cheese fresh. Cold cream or pre-shredded cheese makes the sauce grainy. Taste the sauce for salt before assembling because between the cheese and the broth you might not need much extra.

4. Let it rest after it comes out of the oven so the sauce sets, then slice. For a crispier top sprinkle breadcrumbs or fried onions near the very end of baking or put it under the broiler for one to two minutes while watching closely, and rotate the dish halfway so it browns evenly.