2 tablespoons olive oil
2 1/2 cups low-fat or non-fat milk
3 cups chopped raw baby spinach
1/2 pound Fontina or Monterey Jack cheese, shredded
1 large carrot, peeled and grated
1/4 cup finely grated Parmesan cheese
1 clove garlic, minced
1/4 cup panko bread crumbs
1/2 pound small tubular pasta like elbows, shells or pipette
Heat the olive oil in an oven-safe, heavy-bottomed 12-inch skillet over medium heat until shimmering.
Add the spinach, carrot and garlic and cook for 3-4 minutes, until the spinach is wilted and the carrot has softened.
Stir in the pasta and 2 cups milk and bring to a simmer. Reduce the heat to medium low or low if the milk bubbles too strongly, and cook for about 15 minutes, stirring frequently, until the pasta is al dente and has absorbed most of the milk.
Note: The milk should be steaming and barely bubbling. Add the remaining 1/2 cup milk as needed if the pasta is absorbing the liquid too quickly.
Preheat the oven broiler and turn off the heat to the stove burner. Stir in the Fontina cheese, allowing the residual heat in the pan to melt the cheese completely.
Whisk the Parmesan cheese and panko bread crumbs together in a small bowl. Sprinkle the cheese and bread crumbs evenly over the surface of the mac and cheese, and transfer the pan to the oven.
Broil until the top of the casserole is browned evenly; times may vary based on your broiler, so watch carefully.