Onion Mushroom Gratin

Bree, Baked Bree

One of my favorite side dishes is potato gratin. It is for sure a special occasion side dish, the ultimate in rich and decadent, but so incredibly delicious. Worth every extra minute on the treadmill.

My potato gratin has the addition of sautéed onions and mushrooms and was created with the idea that it would be served next to a steak. I cannot think of a better “meat and potatoes” meal than this one. When making potato gratin, you can reduce the oven time by boiling the potatoes until fork tender before layering them in the dish. If you choose to do this, cook uncovered for 40 to 45 minutes or until bubbly and golden brown.

I like to use a combination of cheeses, I think that it adds a different dimension with each bite. Use what you have in your fridge, this is a great dish to adapt to your taste. Blue Cheese would be wonderful in here, too. Also, make sure that you season generously. Potatoes need a lot of salt and pepper, so taste as you go.

Onion Mushroom Gratin

By Bree


4 tablespoons butter
2 onions, peeled and thinly sliced
8-ounces sliced mushrooms
1 clove garlic
salt and pepper
3 pounds Yukon Gold potatoes, peeled and thinly sliced
4 cups cheese, grated and divided (Gruyere, Fontina, Cheddar, Emmental all are great)
2 1/2 cups heavy cream
2 teaspoons fresh thyme leaves
1/4 teaspoon ground nutmeg
1/4 cup flat leaf parsley, chopped


Heat a large sauté pan over medium heat. Add butter and melt. Add onions and sauté for 3 minutes. Add the mushrooms and continue to cook until the onions are soft and mushrooms are brown, about 10 minutes. Add garlic and cook for 1 minute longer. Season with salt and pepper. Set aside.

Preheat oven to 375°F. Butter a 9×13-inch baking dish. Layer half of the potatoes, half of the onion mixture, and half of the cheese. Repeat. Whisk together cream, thyme, nutmeg, salt and pepper to taste. Pour over gratin.

Cover dish with tin foil and Bake for 40 to 45 minutes, or until a fork comes out easily. Uncover, and bake an additional 30 to 40 minutes, or until golden brown. Let stand for 15 minutes before serving. Sprinkle with parsley.

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  1. stef said:

    It’s weird that “potato” isn’t part of the recipe name