# What You'll Need:
→ Vegetables
01 - 2.5 lbs russet or Yukon Gold potatoes, peeled and thinly sliced
02 - 1 small yellow onion, thinly sliced
→ Dairy
03 - 2 cups whole milk
04 - 1 cup heavy cream
05 - 2 cups sharp cheddar cheese, shredded
06 - 1 cup Gruyère or Monterey Jack cheese, shredded
07 - 4 tbsp unsalted butter
→ Pantry & Spices
08 - 3 tbsp all-purpose flour
09 - 1 tsp garlic powder
10 - 1 tsp salt, plus more to taste
11 - ½ tsp ground black pepper
12 - ¼ tsp smoked paprika
13 - Chopped fresh chives or parsley (optional)
# How To Make It:
01 - Preheat the oven to 375°F. Grease a 9x13-inch baking dish with butter.
02 - In a medium saucepan over medium heat, melt butter. Whisk in flour continuously for 1 to 2 minutes until bubbly but not browned.
03 - Gradually whisk in whole milk and heavy cream. Continue whisking until the mixture thickens, about 3 to 5 minutes.
04 - Stir in garlic powder, salt, black pepper, and smoked paprika. Remove from heat.
05 - Add 1½ cups shredded sharp cheddar and ½ cup shredded Gruyère cheese. Stir until fully melted and smooth.
06 - Arrange half of the sliced potatoes evenly in the prepared baking dish. Top with half of the sliced onions.
07 - Pour half of the cheese sauce evenly over the potatoes and onions layer.
08 - Layer remaining potatoes and onions over the sauce, then cover with the remaining cheese sauce.
09 - Evenly sprinkle the remaining cheddar and Gruyère cheeses over the top layer.
10 - Cover the dish tightly with aluminum foil and bake for 45 minutes.
11 - Remove foil and bake an additional 25 to 30 minutes until potatoes are tender and the top is golden and bubbling.
12 - Allow the casserole to rest for 10 minutes. Garnish with chopped chives or parsley before serving.
