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This Potato Mushroom Boursin Au Gratin has tender slices of potatoes and mushrooms in a creamy and flavorful cheese sauce, topped with buttery bread crumbs. 

Potato Mushroom Boursin Au Gratin

Whether you’re looking for one more delicious side dish to serve with your Thanksgiving turkey later this week, or you are already looking ahead to your Christmas prime rib dinner – this delicious Potato Mushroom Boursin Au Gratin deserves a close look. It’s absolutely delicious!

This isn’t your traditional potatoes au gratin recipe. It’s an amped-up version with flavorful ingredients added at every step of the way – and after one bite of this Potato Mushroom Boursin Au Gratin, your taste buds will be very, very happy!


Potato Mushroom Boursin Au Gratin

How do you make Potato Mushroom Boursin Au Gratin?

You’ll start out by sautéing slices of cremini (or baby bella) mushrooms in butter and extra virgin olive oil. Then a splash of cognac is added to the mushrooms. The alcohol will simmer off, leaving a wonderful flavor behind as the cognac is absorbed into the mushrooms.

Next, you’ll sauté some pancetta until crispy, then add diced onions to the pan – cooking them until they start to get translucent. Next, milk and slices of potatoes are added to the pan – and as the potatoes cook, they pick up that wonderful salty flavor from pancetta and onions.

But – there’s more! Once the potatoes are tender, the mixture is removed from the heat and a generous amount of garlic and herb Boursin cheese (one of my all-time favorite kinds of cheese) is stirred in. The cheese melts and creates a wonderful, rich sauce – plus the potatoes absorb the Boursin flavor too.


Potato Mushroom Boursin Au Gratin

To assemble your Potato Mushroom Boursin Au Gratin – you’ll pour the creamy potato mixture into a baking dish, then layer on the sautéed cognac mushrooms. Before baking, you’ll also add some shredded extra sharp cheddar cheese on top of the mushroom layer, then a sprinkle of buttery panko bread crumbs.

Bake until hot and bubbly, with a golden crispy top.

Potato Mushroom Boursin Au Gratin -


Allow your Potato Mushroom Boursin Au Gratin to sit out of the oven for a bit to set up before serving with your favorite turkey or prime rib meal.

One last note: You can find the garlic and herb flavored Boursin cheese at most supermarkets, typically in the gourmet cheese section. Or you can make it yourself using our Homemade Boursin Cheese recipe here.


You may enjoy these other recipes made with Boursin cheese:

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Potato Mushroom Boursin Au Gratin - A Family Feast

Potato Mushroom Boursin Au Gratin

  • Author: A Family Feast
  • Prep Time: 20 minutes
  • Cook Time: 45 minutes
  • Total Time: 1 hour 5 minutes
  • Yield: 6-8 servings
  • Category: side dish
  • Method: baked
  • Cuisine: French


2 tablespoons butter

2 tablespoons extra virgin olive oil, divided

12 ounces baby bella (cremini) mushrooms, sliced

1 tablespoon cognac

4 ounces pancetta, diced small

1 cup onions, diced

2 pounds Russet potatoes, half-inch diced

3 cups whole milk

2 5.2-ounce boxes garlic and herb Boursin cheese

2 tablespoons butter

1 cup panko bread crumbs

1 cup cheddar cheese, shredded


In a large skillet over high heat, melt the two tablespoons of butter in one tablespoon of the olive oil. Once hot and frothy, add mushrooms and cook over high heat until browned, about five minutes. Add cognac off the heat and then return the pan to the heat to evaporate the alcohol. The mixture may flame, that is fine.

Remove to a plate to cool and lay the mushrooms flat. Stacking them in a bowl will make them give up water.

Heat the pan back to medium high and add the remaining tablespoon of oil. Once hot add the pancetta.

Cook the pancetta to crisp then add the onions. Sauté for three minutes and add the potatoes and milk.

Cover and simmer for 8 minutes,* stirring every 3-4 minutes or until cooked through. Remove from heat and stir in the Boursin cheese.

*While potatoes are cooking, make topping by melting the two tablespoons of butter in a small sauce pan over medium high heat and add the panko bread crumbs.  Toss and stir for a few minutes to brown then remove from heat and set aside.

Preheat oven to 350 degrees F.

To assemble, pour potato mixture into a 9x9x2½-inch casserole dish. Top with the reserved mushrooms then top with the shredded cheddar and the toasted bread crumbs.

Bake for 20 minutes with a piece of foil on the rack below the dish to catch any drips.

When the au gratin is right out of the oven, it will be loose and as it sets, it will firm up.

Keywords: potatoes au gratin, potato casserole



Potato Mushroom Boursin Au Gratin

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