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–+ servings
scalloped au grain potato recipe in baking dish
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5 from 1 vote

Creamy Scalloped Au Gratin Potatoes with Squash + Onion

Our delicious creamy scalloped Potatoes Au Gratin with onion and squash uses sweet potatoes and russet potatoes. It's a delicious, creamy side dish recipe.
Prep Time20 minutes
Cook Time1 hour
Total Time1 hour 20 minutes
Course: holiday recipes, Side Dishes
Cuisine: American
Servings: 8
Author: This Worthey Life

Ingredients

  • 4 medium russet potatoes peeled and thinly sliced (1/8 inch)
  • 2 large sweet potatoes peeled and thinly sliced (1/8 inch)
  • 1 large sweet onion thinly sliced
  • 1 large yellow squash thinly sliced
  • 1 tsp sea salt
  • 1/2 tsp freshly ground black peppercorns adjust to taste
  • 1/2 tsp smoked paprika adjust to taste
  • 1/4 tsp onion powder adjust to taste
  • 3 tsp all-purpose flour
  • 3 tsp unsalted butter
  • 2 1/4 cups half-n-half
  • 2 cups freshly grated white cheddar
  • 1/2 cup grated pecorino cheese or a good Parmigiano Reggiano divided
  • 2-3 tbsp of chopped curly or flat-leaf parsley

Instructions

  • Preheat oven to 350°F. Wash and peel the potatoes. Adjust a mandoline slicer to 1/8 and slice the russet potatoes, sweet potatoes, yellow squash, and onions.
  • Alternate the slices in an 8" x 10" baking dish and set aside.
  • Make the cream sauce. Place a large skillet over medium-low heat and add 3 tablespoons of unsalted butter.
  • When the butter is melted, whisk in 3 tablespoons of all-purpose flour. Whisk the mixture until the roux becomes a light blond color. Whisk in the half and half.
  • Add the grated white cheddar cheese a little at a time until it is fully incorporated.
  • Whisk in the sea salt, freshly cracked black peppercorns, onion powder, and smoked paprika.
  • Reduce the heat to low and cook until the mixture coats the back of a spoon.
  • Pour the mixture over the sliced potatoes, squash, and onions.
  • Scatter about half of the grated pecorino cheese over the potatoes, squash, and onions.
  • Cover the dish tightly with foil and Place the dish in the 350°F oven on the center rack and bake for 45 minutes, until the potatoes are fork-tender.
  • Remove the foil and continue baking for another 15 minutes to lightly brown and thicken the top.
  • Remove the potato dish from the oven and evenly scatter the remaining grated pecorino cheese on top, finishing with chopped parsley.
  • Serve.
  • Note: If your squash is very moist, lightly salt and pat dry before layering.
  • For a deeper golden crust, broil the top for about 1-2 minutes at the very end. You will need to stand and watch this so your dish doesn’t burn!
  • Slice thickness impacts the baking time. Check tenderness before removing from the oven.