Cheesy Baked Cauliflower

Name: Cheesy Baked Cauliflower
Ingredients: 2 large heads ( 10 cups ) cauliflower , cut into bite-sized florets; 1 tablespoon olive oil or vegetable oil; 8 ounces sharp cheddar cheese , grated; 4 ounces Monterey Jack cheese , grated; 1 tablespoon cornstarch; 4 tablespoons unsalted butter; 1/4 cup all-purpose flour; 1 1/2 cups whole milk; 1/2 cup heavy cream; 3/4 teaspoon kosher salt; 1/2 teaspoon paprika; 1/2 teaspoon garlic powder; 1/4 teaspoon ground black pepper; 1/4 teaspoon mustard powder; 1/4 teaspoon turmeric