Preheat your oven to 350°F and grease an 8x8-inch baking dish.
Cook the macaroni according to the package directions, then drain well. If you plan to freeze it, cook the noodles just slightly less than the package says so they don't get soggy.
While the pasta cooks, melt the butter in a medium saucepan over medium heat. Whisk in the flour and cook, stirring, until the mixture is bubbly, about 1 minute.
Slowly add the milk, stirring constantly until the sauce thickens. Stir in the salt and Worcestershire sauce and cook for 1 more minute.
Remove the pan from the heat and add the cheddar, mozzarella and 1/4 cup Parmesan. Return the pan to low heat and stir until the cheese is completely melted.
Stir in the cooked macaroni until it's coated, then spread it into the prepared baking dish.
For the crumb topping, tear the bread into small pieces and pulse in a food processor until you have about 1 cup of crumbs. Stir in the melted butter and the remaining 1/4 cup Parmesan, then sprinkle it evenly over the mac and cheese.
Bake for 20-30 minutes, until hot and bubbly and the topping is browned to your liking.