Potato and Winter Squash Gratin

This method for potatoes au gratin takes all of the guesswork out of baking the potatoes and ensures perfectly-cooked spuds and a glossy, silky, cheesy sauce.

Cuisine

European

Difficulty

Easy

Duration

30 Minutes

Diet

Vegetarian, Gluten-Free, Celiac, Egg-Free

Cooking Technique

Sauté, Pressure Cook, Bake, Broil

Keywords

Baked Potato Casserole, Instant Pot Culinary Team, Instant Pot® Rio Wide, Potato au Gratin, Side Dishes

Prep Time

10 Minutes

Cook Time

20 Minutes

Servings

6-8 Servings

Ingredients

4 tablespoons unsalted butter
8 garlic cloves, smashed and peeled
1 shallot, peeled and quartered
Kosher salt
Freshly ground pepper
3 pounds Russet Potatoes, scrubbed, peeled, and cut into ¼-inch rounds
2 cups whole milk
1 cup heavy cream
2 bay leaves
1 pound winter squash, such as Honeynut, peeled, halved, and cut into ¼-inch slices
1 cup water
6 ounces sharp white cheddar, coarsely grated, divided
½ cup freshly grated Parmigiano Reggiano
¼ cup finely sliced chives, for serving

Instructions

In the Instant Pot® Rio Wide, melt the butter on the saute setting over medium heat. When the butter is foaming, add the garlic and shallot and season with salt and pepper. Cook, stirring, until the garlic is softened and the shallot is starting to brown at the edges, about 5 minutes.
Add the potatoes and stir well to coat the potatoes with butter and combine ingredients. Season again with salt and pepper, then pour in the milk and heavy cream.
Add the bay leaves, seal the lid and Pressure Cook on High for 2 minutes.
Manually release the steam, then open the lid and use a slotted spoon to transfer the cooked potatoes to one side of a rimmed baking sheet, leaving the cooking liquid in the pot. (Leave room on the baking sheet for the squash.)
Stir in 1 cup water, then add the squash and season sparingly with salt and pepper.
Seal the lid and Pressure Cook on High for 1 minute.
Manually release the steam, then open the lid and use a slotted spoon to transfer the cooked squash to the other side of the rimmed baking sheet with the potatoes., leaving the cooking liquid in the pot.
Strain the cooking liquid through a fine mesh strainer into the same measuring glass used for the milk and cream, pressing on solids to extract as much liquid as possible. Set aside; reserve Inner Cooking Pot.
Preheat oven or toaster oven to 450°F / 230°C . Line a rimmed baking sheet with aluminum foil.
Spoon any partially broken slices of potato and squash into a 3-quart casserole dish. Alternating as desired, shingle the remaining potato and squash into the dish, arranging them at about a 45-degree angle. Set aside.
Pour the strained liquid into the Inner Cooking Pot, then return to the Cooker Base. Set the Instant Pot to Sauté on Medium and bring the liquid to a simmer.
Whisking constantly, add the Parmigiano and whisk until melted, 1 minute. Add 4 ounces of the cheddar and whisk until the cheese is completely melted.
Pour the cheese sauce over the potatoes and squash in the dish, then tap the dish on the surface to remove any air bubbles and encourage mixture to flow to the bottom of the dish.
Top with remaining 2 ounces cheddar cheese.
Place casserole dish on prepared baking sheet and bake gratin on the middle rack until the cheese is completely melted and the liquid is bubbling, 10 to 15 minutes.
Heat the broiler and broil gratin until the cheese is melted, browned, and bubbling, about 3 minutes.
Remove gratin from the oven and let sit until bubbling subsides, about 3 minutes. Top with chives before serving.