Greek Mac and Cheese

Name: Greek Mac and Cheese
Ingredients: 3 slices crustless white bread, torn into small pieces; 9 tbsp. unsalted butter, melted; Kosher salt, to taste; 8 oz. hollow pasta, preferably elbow macaroni; 1⁄4 cup flour; 3 cups milk; 4 cups grated graviera or kefalotyri cheese (about 12 oz.); 3⁄4 tsp. ground cinnamon; 1⁄8 tsp. freshly grated nutmeg; Freshly ground black pepper, to taste; 2 tbsp. extra-virgin olive oil; 8 large shallots, finely chopped; 16 oz. baby spinach, roughly chopped; 8 scallions cut into 1/4″-thick rounds; 1⁄3 cup roughly chopped fresh dill; 1 3⁄4 cups crumbled feta (about 8 oz.)