Truffle Mushroom Gruyère Scalloped Potatoes for the Holidays Step-by-step instructions

Before you start

Before starting, slice the potatoes thinly—about 1/8 inch thick. A mandoline makes this easy and ensures even cooking. Sauté the mushrooms in a skillet until they release their liquid and start to brown.

Have all the ingredients measured and ready. The slow cooker should be clean and dry. No need to preheat it; the heat will build gradually.

Instructions

Sauté and Prep

1. 1Sauté the Mushrooms
   In a large skillet over medium-high heat, melt 1 tablespoon of the truffle butter. Add the sliced chanterelle and cremini mushrooms and cook, stirring occasionally, until they release their moisture and begin to brown, about 8 minutes. Season with a pinch of salt and pepper. Remove from heat and set aside.
   Look for The mushrooms should be golden and any liquid has evaporated.
   Tip Do not overcrowd the pan; cook in batches if needed to ensure even browning.
2. 2Prepare the Cream Mixture
   In a medium bowl, whisk together the heavy cream, remaining truffle butter (melted), fresh thyme leaves, 1/2 teaspoon of salt, and 1/4 teaspoon of pepper. Set aside.
   Look for The cream mixture should be smooth and well combined.
   Tip Melt the truffle butter gently in the microwave or on the stovetop before whisking.

At the end of this phase, the mushrooms should be golden-brown and fragrant, with no excess liquid in the skillet. The cream mixture should be smooth and well blended. The potatoes are sliced and ready to layer. The kitchen smells of truffle and thyme, promising a decadent dish to come.

Layer and Pour

3. 3Layer the Potatoes
   Spread one-third of the sliced Yukon Gold potatoes evenly over the bottom of a 6-quart slow cooker. Top with half of the sautéed mushrooms, then sprinkle with one-third of the shredded Gruyère. Repeat the layers: potatoes, mushrooms, cheese, then finish with a final layer of potatoes and the remaining cheese.
   Look for The layers should be evenly distributed, with the last layer of potatoes covered in cheese.
   Tip Use a mandoline to slice the potatoes uniformly, about 1/8-inch thick, for even cooking.
4. 4Pour the Cream Mixture
   Pour the prepared cream mixture evenly over the layered potatoes and mushrooms. Gently press down with a spatula to ensure the cream seeps through all the layers.
   Look for The cream should just about cover the top layer of potatoes.
   Tip If the potatoes are not fully submerged, add a little extra cream or milk to cover.

The slow cooker is filled with even layers of potatoes, mushrooms, and cheese, with the cream mixture poured over the top. The cream should just cover the top layer.

The dish looks like a work of art, with the yellow cheese and dark mushrooms peeking through the cream. Press down gently to ensure the cream reaches the bottom.

Slow Cook and Finish

5. 5Slow Cook on Low
   Cover the slow cooker with the lid and cook on LOW for 4 1/2 hours, until the potatoes are tender and the top is golden and bubbly. Do not lift the lid during the first 3 hours of cooking to maintain even heat.
   Look for The edges will be bubbling and the top nicely browned.
   Tip If the top is not golden after 4 1/2 hours, turn the slow cooker to HIGH for an additional 30 minutes.
6. 6Rest and Serve
   Once cooked, turn off the slow cooker and let the potatoes rest, uncovered, for 10 minutes. This allows the sauce to thicken slightly. Serve warm, garnished with fresh thyme leaves and shaved Parmesan.
   Look for The sauce should cling to the potatoes, not be watery.
   Tip Use a large spoon to serve, scooping from the bottom to get all the layers.

After 4 1/2 hours on low, the top is golden and bubbly, and the potatoes are tender when pierced. The aroma is intensely savory, with notes of truffle and roasted cheese. The edges are caramelized, and the sauce is thick and creamy. After a 10-minute rest, the gratin holds its shape when served.

Common mistakes

One common mistake is lifting the lid during cooking, which lets out heat and extends the cooking time. Trust the recipe and resist the urge to peek. Another issue is slicing potatoes too thick, which results in crunchy centers.

Use a mandoline or sharp knife to slice uniformly. Also, do not skip sautéing the mushrooms—raw mushrooms release water and make the sauce thin. Finally, make sure the cream covers the potatoes; if not, add a little extra.

How to tell it’s done

The scalloped potatoes are done when a knife easily pierces the center of the potatoes with no resistance. The top should be golden brown and the edges bubbling. The sauce should be thick and creamy, not watery.

If the top is not browned after the cooking time, turn the slow cooker to HIGH for an additional 20-30 minutes, watching closely. Let rest for 10 minutes before serving to allow the sauce to set slightly.