Sourdough Au Gratin Potatoes Recipe

Sourdough Au Gratin Potatoes in a baking dish.

Yield:

Prep Time: 30

Cook Time: 1 30

Total Time: 2

Perfectly creamy, cheesy, and flavorful, these are Sourdough Au Gratin Potatoes at their very best! Sourdough discard is used to thicken the cream sauce. Cover and bake for the most tender and cheesy potatoes - perfect for any holiday table.

4.80 from 5 votes

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Equipment

Ingredients

2 1/2 pounds Gold Yukon Potatoes about 6-7, 1/8-inch slices
1/2 small onion about 1/2 cup, thinly sliced
2 cups whole milk 470g
1/2 cup heavy cream 100g
1/4 cup sourdough discard 70g
1 cup cheddar cheese 113g or 4 oz, shredded
1 cup Gruyere cheese 120g, shredded
1/4 cup Parmesan cheese 20g
1/2 teaspoon garlic powder
salt and pepper to taste

Instructions

Preheat your oven to 400 degrees F. Grease a 2.5 - 3 quart casserole dish with butter and set aside.
First, scrub the potatoes (peeling is optional!) and thinly slice them into 1/8-inch thick slices. You could also use a food processor or mandoline for quick work of slicing.
2 1/2 pounds Gold Yukon Potatoes, 1/2 small onion
Slice half of a small onion as thin as possible. Add the sliced potatoes and onions to a large bowl and set aside.
In a medium bowl, whisk together the milk, heavy cream, and sourdough discard until smooth. Pour the mixture into a medium saucepan and heat to medium heat. Stir occasionally. Continue to cook until the sauce thickens and begins to bubble. Remove from the heat.
2 cups whole milk, 1/2 cup heavy cream, 1/4 cup sourdough discard
To the white sauce, add the grated cheddar cheese, half of the grated Gruyere cheese, garlic powder, and salt and pepper to taste. Stir until the cheese is fully melted and smooth.
1 cup cheddar cheese, 1 cup Gruyere cheese, 1/2 teaspoon garlic powder, salt and pepper
Pour the cheese sauce over the sliced potatoes and onion. With a wooden spoon, stir until the vegetables are fully coated in the cheese sauce.
Pour the potato mixture into the prepared baking dish and spread evenly in a single layer. Top the potatoes with the remaining grated Gruyere and grated Parmesan cheese, then cover the baking dish with aluminum foil and place in the preheated oven to bake for 60 minutes.
1/4 cup Parmesan cheese
Next, remove the foil and continue to cook for an additional 15-30 minutes or until the topping is golden brown and the potatoes can be easily pierced with a fork.
Allow the Sourdough Au Gratin to rest for 15 minutes before serving. Garnish with chopped parsley, chives, or thyme leaves, and serve warm. Enjoy!

Notes

This recipe card was updated on 03/04/26.

How to Serve

Sourdough Au Gratin is the perfect side dish for any special occasion, like Easter or Christmas dinner. Serve this creamy and delicious potato recipe alongside a salty slice of honey ham or a juicy cut of prime rib for an exceptional dining experience. Don't forget to pass the Sourdough Dinner Rolls!

How to Store

Store leftover Sourdough Au Gratin in an airtight container in the fridge for up to 4-5 days.

To reheat, place the casserole dish covered in foil in a 350-degree oven for about 15-20 minutes, or until heated throughout.

FAQs:

What is the difference between Scalloped Potatoes and Au Gratin Potatoes?

While both are popular potato dishes, the main difference between scalloped potatoes and au gratin potatoes is the inclusion of cheese. Scalloped Potatoes are a creamy and tender baked potato dish, while Au Gratin Potatoes are covered in a cheesy, cream sauce with a crispy cheese crust on top.

Can I use different types of cheeses for Sourdough Au Gratin?

This Sourdough Au Gratin recipe uses a combination of cheeses like Cheddar Cheese, Gruyere cheese, and Parmesan cheese. If preferred, you could use only one type of cheese for the whole dish or substitute it with other delicious grated cheeses, like white cheddar cheese or asiago.

Can Sourdough Au Gratin be made in advance?

Not only is this potato side dish easy and delicious but it can also be made in advance! Save yourself some time by preparing the creamy potatoes up to 24 hours in advance. Prepare the recipe until it's ready to bake. Instead, cover the baking dish with aluminum foil and store it in the fridge. Bake for an additional 10-15 minutes than the original recipe.

Nutrition

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