Making a Scalloped Potato Gratin is so easy and so incredibly delicious that you’ll want to make them all the time. The flavor options are endless. One of my favorite gratin potato dishes is to add roasted Poblano peppers. They give the dish a slightly smokey flavor.
Today, I’m making them with thinly sliced onions. Let me show you a few simple steps to making a Scalloped Potato Gratin.
Off the heat, I add in some fresh chopped chives and freshly grated cheese to the sauce. Here I’m adding a mixture of grated white cheddar and some yellow cheddar for color. I’m saving some back for the top. this way the potato gratin will have a nice golden crust. I make sure to add the cheese in slowly to the sauce, mixing it with a wooden spoon, until all the cheese has melted.
Prep Time: 30 minutes (includes the parboiling the potatoes)
Cook Time: 1 hour, uncovered
Total Time: 1 hour 30 minutes
Yields: 6 servings
Equipment: 1 (6-quart) saucepot, 2 (3-quart) saucepans, 1 (9 x 9) 2-quart baking dish, box grater, Mandolin, Microplane
5 cups (2-pound) bag of baby Yukon gold potatoes, parboiled and sliced 1/8-inch thick, 5 cups
1 large sweet onion, thinly sliced
6 tablespoons of butter, unsalted, 3 tablespoons to grease the baking dish
3 tablespoons of all-purpose flour
1 cup of whole milk, warm
1 cup of half-and-half, warm
1 1/2 tablespoons plus 1 teaspoon of Kosher salt
1/2 teaspoon of freshly ground black pepper
1 teaspoon of smoked paprika
1/2 teaspoon of garlic powder
1/2 teaspoon of onion powder
1/4 teaspoon of cayenne pepper
1 pinch of nutmeg, freshly grated
3/4 cup of white cheddar, (Cabot) freshly grated
1/4 cup of Colby Jack cheese (Cabot) freshly grated, reserve 1/2 cup for topping
1/4 cup Parmesan cheese, freshly grated for topping
2 tablespoons of fresh chives, minced
1/4 cup of Italian flat-leaf parsley, finely chopped
Preheat oven to 350-degrees F.
First, generously butter the casserole dish.
Second, slice one large onion using a Mandolin and grate the cheese.
Third, parboil the Yukon gold potatoes until just fork tender.
Start by placing the potatoes into a large saucepot. Cover the potatoes with cold water. Over medium heat, bring the potatoes up to a boil. Once they are boiling, add 1 1/2 tablespoon of Kosher salt and continue cooking for 15 to 20 minutes. Take a paring knife and stick it into the center of one of the largest potatoes. If there is still some resistance removing the knife, that’s fine, turn the heat off. Drain and allow the potatoes to cool before slicing, around 10 minutes.
Note: Time may vary depending on the size of the potatoes.
Once the potatoes have cooled down enough to handle, use a Mandolin to slice the potatoes. Transfer the sliced potatoes to a large mixing bowl. Set aside.
In a small saucepan over medium heat add half-and-half, whole milk, cayenne pepper, smoked paprika, onion powder, garlic powder, Kosher salt, and fresh ground black pepper. Bring the liquid to the *scalding point. Turn the heat off.
In another saucepan over medium-low heat melt 3 tablespoons of unsalted butter. Once that’s melted, add the flour, Whisk the flour into the butter until paste-like and smooth. Add the warm milk mixture. Continue to whisk until the sauce thickens, about 5 to 7 minutes. Don’t rush the process, you’ll know when the sauce has reached the perfect thickness when it coats the back of a spoon. Add the minced chives. Stir to combine.
Place a layer of the potatoes topped with half of the sliced onions. Pour half the milk sauce over the potatoes then top with half the cheese mixture. Repeat doing a second layer the same way, finishing with the remaining sauce and grated cheese mixture. Sprinkle the top with freshly grated Parmesan. Finally, add finely chopped flat-leaf parsley over the top. Bake for 1 hour until bubbly and golden brown. Allow the dish to rest for 10 to 15 minutes before slicing. There you have it, my Scalloped Potato Gratin.
*Scalded Milk is milk heated to a near boil. Small bubbles will start to appear around the rim of the pot.