Pre-heat the oven to 400F (200C). Grease well a medium-sized baking pan 10 x 8 inches (26 x 20 cm) or use an oven safe skillet. At least 2 inches (4½cm) deep.
In a large pot of salted boiling water cook the pasta until very al dente, drain well, but do not rinse.
In a small bowl mix together the bread crumbs, 1½ tablespoons Parmesan cheese and chopped parsley, set aside.
In a large pot over low-medium heat, melt the butter, add the flour and salt, whisk well together, then add the mustard and the milk, whisk until smooth and thickened, then add the cheddar and Parmesan cheese, stir until almost completely melted, add the cooked macaroni and gently stir to combine, pour into prepared baking pan, top with the crumb mixture, bake until browned, approximately 25 minutes. Let sit 3-5 minutes before serving. Enjoy!
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Notes
I used sharp white cheddar cheese and it was delicious.Store leftovers in an airtight container in the refrigerator for up to 3 days. Reheat in the microwave. Add a splash of milk as needed to rehydrate pasta.