If there is one side dish that can truly steal the spotlight from the main roast, it’s this Potato and Mushroom Gratin. Imagine layers of buttery Yukon Gold potatoes, infused with heavy cream and earthy thyme, then topped with golden, garlic scented mushrooms. It is rustic, elegant, and the definition of comfort food.
The Story Behind the Gratin
In American households, a good potato gratin is more than just a side dish; it’s a holiday tradition. Whether it’s for a cozy Thanksgiving dinner or a sophisticated Sunday roast, this recipe hits all the right notes. The inspiration comes from the classic French Gratin Dauphinois, but with a modern, earthy twist by adding crimini mushrooms and plenty of fresh garlic.
Flavor Profile: The Yukon Gold potatoes provide a natural buttery richness, while the Parmesan adds a sharp, salty bite. The real magic happens when the mushrooms roast on top, soaking up the garlic and thyme aromas, creating a savory depth that will have your guests asking for seconds (and thirds!).
Expert Tips for Success
- Slice it Thin: For the best texture, use a mandoline slicer to get those potatoes to a consistent 1/8 inch thickness. This ensures even cooking and beautiful layers.
- The Potato Choice: Stick with Yukon Gold. They have a medium starch content that holds its shape while still becoming incredibly creamy. Russets tend to fall apart too much for this style of gratin.
- Don’t Skimp on the Cream: If the potatoes look a bit dry at the 45 minute mark, don’t be afraid to add a tablespoon or two more of heavy cream. You want that luxurious, silky finish!
Make Ahead & Storage Instructions
Can I make this ahead? Absolutely! This is one of those rare dishes that tastes even better the next day.
- To Store: Let the gratin cool completely in the dish. Cover tightly with foil and refrigerate for up to 24 hours.
- To Rewarm: Cut the gratin into pieces and place them on a rimmed baking sheet. Cover with foil and heat in a 350°F oven for about 10-15 minutes until warmed through and the cheese is bubbly again.
Ingredient Substitutions
- Mushrooms: If you can’t find Crimini (Baby Bellas), regular white button mushrooms work fine, or you can go fancy with Chanterelles or Shiitakes for a wild mushroom twist.
- Dairy Free: You can substitute the heavy cream with full fat canned coconut milk, though it will add a slight coconut hint. Nutritional yeast can replace the Parmesan for a vegan friendly umami kick.
- Herbs: No fresh thyme? Fresh rosemary is a great alternative, but use half the amount as it is more pungent.
Serving Suggestions
This gratin is the perfect partner for a Garlic Herb Roasted Chicken or a Reverse Seared Ribeye Steak. For a balanced meal, serve it alongside something bright and acidic, like a Lemon Arugula Salad or blanched green beans with a squeeze of lemon.
Frequently Asked Questions (FAQ)
Do I need to peel the potatoes?
Yes, for this specific recipe, peeling the Yukon Golds provides a much more refined and creamy mouthfeel.
Can I use an Air Fryer?
It’s not recommended for the initial baking as you need the even heat of an oven to cook through the dense layers of cream and potato. However, you can use an air fryer to reheat individual slices for a crispy edge!
Creamy Potato and Mushroom Gratin with Garlic & Thyme
Equipment
- 13x9x2 inch glass or ceramic baking dish
- Mandoline slicer optional but recommended
- Medium mixing bowl
- Pastry brush
Ingredients
- 5 tbsp olive oil divided
- 6 garlic cloves thinly sliced
- 3/4 tsp freshly ground black pepper plus extra for mushrooms
- 2 1/2 lbs medium Yukon Gold potatoes peeled and sliced 1/8 inch thick
- 1 1/2 tsp coarse kosher salt plus extra for mushrooms
- 1 1/4 cups or more heavy whipping cream, divided
- 12 oz fresh crimini baby bella mushrooms, sliced
- 1 cup freshly grated Parmesan cheese divided
- 2 tbsp chopped fresh thyme
Instructions
- Prep the Base: Preheat oven to 375°F. Brush your baking dish with 2 tbsp of olive oil.
- Layer the Potatoes: Arrange 1/3 of the potatoes in the dish, slightly overlapping. Sprinkle with 1/2 tsp salt and 1/4 tsp pepper. Pour 1/3 cup cream over them and sprinkle with 1/4 cup Parmesan.
- Repeat Layers: Repeat this process two more times (3 layers total).
- First Bake: Bake uncovered for 45 minutes or until potatoes are tender. If they look dry, add a splash more cream.
- Prep Topping: In a bowl, toss sliced mushrooms with 3 tbsp olive oil, salt, and pepper.
- Final Bake: Sprinkle sliced garlic and thyme over the gratin. Arrange mushrooms around the edges. Drizzle with the remaining 1/4 cup cream and 1/4 cup Parmesan.
- Finish: Bake for another 20 minutes until mushrooms are tender and edges are golden brown.
- Rest: Let rest for 10 minutes before slicing to allow the cream to set.
