Spinach Mac and Cheese

Name: Spinach Mac and Cheese
Ingredients: Cooking spray; 1 teaspoon kosher salt plus more for salting the pasta water; 1 pound small elbow macaroni; 1/4 cup unsalted butter; 1 large shallot , minced; 1/4 cup all-purpose flour; 4 cups cold milk; 12 ounces Gruyère cheese , grated; 1 cup shredded Parmesan , divided; 1/4 teaspoon freshly grated nutmeg; 1/8 teaspoon ground cayenne pepper; 3 ( 10 ounce ) boxes frozen chopped spinach , thawed and squeezed very dry; 3/4 cup panko breadcrumbs; 1/4 cup olive oil