# Ingredient List:
→ Vegetables
01 - 3.3 pounds russet or Yukon gold potatoes, peeled and thinly sliced
02 - 1 medium yellow onion, finely chopped
→ Dairy
03 - 2 cups whole milk
04 - 1 cup heavy cream
05 - 2 cups shredded sharp cheddar cheese
06 - ½ cup grated Parmesan cheese
07 - 4 tablespoons unsalted butter
→ Pantry
08 - 3 tablespoons all-purpose flour
09 - 1 teaspoon salt
10 - ½ teaspoon black pepper
11 - ¼ teaspoon ground nutmeg (optional)
# How to Make:
01 - Preheat oven to 375°F. Grease a 9x13 inch baking dish with butter or nonstick spray.
02 - Melt butter in a medium saucepan over medium heat. Add finely chopped onions and cook until translucent, about 4 minutes.
03 - Sprinkle flour over onions and stir constantly for 1 minute to form a roux.
04 - Gradually whisk in whole milk and heavy cream. Bring to a gentle simmer, stirring frequently, until the sauce thickens, about 3 to 5 minutes.
05 - Stir in salt, black pepper, nutmeg if using, and half of the shredded cheddar and grated Parmesan. Remove from heat when the cheese has melted and sauce is smooth.
06 - Arrange half of the potato slices evenly in the prepared baking dish. Pour half of the cheese sauce over the potatoes.
07 - Repeat with remaining potato slices and cheese sauce. Sprinkle the remaining cheddar and Parmesan cheese on top.
08 - Cover the dish tightly with aluminum foil and bake for 40 minutes.
09 - Remove foil and continue baking for an additional 20 minutes, until potatoes are tender and the top is golden and bubbly.
10 - Allow to rest for 10 minutes before slicing to ensure easier serving.
