Vidalia Onion & Potato Au Gratin

The perfect side dish for any holiday gathering! Food Network Chopped Champion Shannen Tune shows you how to make a delicious and simple sweet onion & potato au gratin casserole.

  • 4 to 5 russet potatoes, sliced ¼-inch thick
  • 2 Vidalia onions, sliced and caramelized  
  • 2 cups whole milk
  • 16 oz cheddar jack cheese, shredded
  • 2 Tbsp all-purpose flour
  • 2 Tbsp unsalted butter
  • 2 Tbsp ground parmesan cheese
  • salt & pepper to taste


  1. Start by caramelizing your 2 onions, sliced, using this caramelized sweet onions recipe. Or, check out this blog post for instructions on caramelizing onions using an Instant Pot or slow cooker. 
  2. Once your onions are caramelized, place sliced potatoes in a pot and cover with cold water. Bring water to a boil and cook for 5 minutes. Drain water and cool potatoes.
  3. In a small saucepan melt butter and add flour to make a roux. Mix until it looks like wet sand. Add one cup of milk to roux and whisk together. After milk and roux are mixed and the milk is warm, add the rest of the milk and season with salt and pepper. Allow this bechamel sauce to simmer for 20 minutes and stir continuously so that it doesn’t burn.
  4. Spray the baking dish with nonstick spray and layer half of the potatoes. Top the first layer of potatoes with caramelized onions and half of the cheddar-jack cheese. Layer the cheese with the rest of the potatoes, then top with the bechamel sauce, parmesan cheese and the rest of the cheddar-jack cheese.
  5. Bake in oven at 350°F (177°C) for 25 minutes, or until the cheese begins to bubble and brown. Allow to cool before cutting into the casserole. 

If you like this recipe, try our Green Bean Casserole with Fried Sweet Onions!

Prep Time

15 minutes

Cook Time

25 minutes