Potato & Mushroom Gratin

A traditional gratin, reconsidered according to what was already in the

refrigerator.

There are recipes one plans carefully, and others that begin by opening the refrigerator.

This gratin belongs to the latter category.

The foundation is traditional: thinly sliced potatoes, cream, butter, garlic and cheese, baked

slowly until the potatoes become tender and the surface develops a deep golden crust. The

variation came from what I had on hand—white button mushrooms, Emmentaler and

Provolone cheese—which turned a familiar potato gratin into something rather more substantial.

The mushrooms are first sautéed in butter until their liquid has reduced considerably. That

concentrated mushroom liquor is then added to the cream and milk rather than discarded,

carrying its flavour back through the potatoes as the gratin cooks.

The result is rich, earthy and deeply comforting. It can accompany a roast or a simple green

salad, although it is substantial enough to occupy rather more of the plate than a side dish usually does.

Potato & Mushroom Gratin

Serves: 6 as a dinner portion or 8 as a lunch portion

Baking dish: 11 × 14 × 2½-inch rectangular ceramic baking dish

Oven: 350°F to begin

Ingredients

• White potatoes, approximately 2½ inches in diameter, enough to fill the baking dish

• 4 cups white button mushrooms, sliced

• ¼ cut water for cooking the mushrooms

• 2 cups 35% heavy cream

• 1 cup whole milk

• 2 cloves garlic, minced

• 7 tablespoons butter, divided ( 3 tbsp for baking dish, 4 tbsp for mushrooms)

• ⅛ teaspoon ground nutmeg

• 8 oz Emmentaler cheese, grated

• 8 oz Provolone cheese, grated

• Salt, to taste

• Finely ground black pepper, to taste

Preparation

Prepare the mushrooms.

Place the sliced mushrooms in a sauté pan with ¼ cup water and 4 tablespoons of the butter.

Cook until the mushrooms have released their moisture and the liquid has reduced to

approximately ¼ cup.

Using a slotted spoon, transfer the mushrooms to a bowl and set aside. Reserve the reduced mushroom and butter liquid.

Prepare the potatoes.

Wash and peel the potatoes, then slice them on a mandoline to approximately ⅛-inch thickness.

Do not rinse the potatoes after slicing. Their natural surface starch helps the cream thicken as the gratin cooks.

Set aside.

Prepare the cheese.

Combine the grated Emmentaler and Provolone in a bowl mix and set aside.

Prepare the cream mixture.

Combine the heavy cream, whole milk, reserved mushroom reduction and nutmeg. Set aside.

Assemble the Gratin

Preheat the oven to 350°F.

Use the remaining 3 tablespoons of butter to generously coat the bottom and sides of the ceramic baking dish. Scatter the minced garlic evenly over the bottom.

Arrange a layer of sliced potatoes over the garlic. Season lightly with salt and finely ground

black pepper.

Add a layer of mushrooms.

Continue alternating the potatoes and mushrooms, seasoning the potato layers lightly as you go.

Depending upon the potatoes and the dimensions of the dish, you should have approximately three layers of potatoes with two layers of mushrooms between them, finishing with potatoes on top.

Spread the combined grated cheeses evenly over the final potato layer.

Slowly pour the cream mixture across the surface, distributing it as evenly as possible over the cheese and potatoes.

Bake. ( total bake time is 1 1/2 Hours )

Bake at 350°F for the first 30 minutes.

Reduce the oven temperature to 325°F and continue baking for another 30 minutes.

Reduce the temperature once more to 300°F and bake for approximately 30 minutes longer, or until the potatoes are completely tender and the cream has substantially reduced.

Much of the surface browning occurs during the first stage of baking. Reducing the temperature gradually allows the potatoes to continue cooking without allowing the cheese to brown too aggressively.

In my oven, I used bottom heat only during the final 30 minutes. As ovens vary, watch the gratin rather than the clock: the top should be richly golden, the cream should be reduced and bubbling gently around the potatoes, and a knife inserted through the centre should meet no resistance.

Allow the gratin to settle briefly before serving.

At the Table

Served warm from its ceramic baking dish, this is the sort of food that requires very little

embellishment. A crisp green salad would provide the necessary counterpoint; roast chicken or beef would make it decidedly more ceremonial.

As for the calorie count, I have no idea.

There are two cups of cream, seven tablespoons of butter and a pound of cheese.

Who’s counting?