Boil the pasta according to package directions. Drain well. Reserve some of the boiling water which is so useful for thickening the sauce.
While the pasta boils, clean the prawns. Pry off the heads (I froze them so I can use them for a Southeast Asian soup that I’ve been dying to make but can’t eat anyway) and peel off the shells together with the tails. Take a prawn, slit the back and pull off the black threadlike thing that runs along its length. That’s its digestive system with all its partially digested food so you don’t really want to eat that. Do the same with all the prawns. You can see the illustrated version of how to to clean, peel and devein shrimps.
Heat the butter in a pan. Add the chopped onion and cook gently until translucent.
Add the asparagus and cook for a minute.
Add the prawns. When the prawns start to change color, pour in the milk and pasta water. Add the cheeses. Season with salt and pepper. By the time everything boils, the cheeses will melt and once and the prawns will finish cooking. If you wait for the prawns to cook through before adding the rest of the ingredients, your prawns will get overcooked and turn tough. It never pays to overcook seafood.
Add the pasta to the sauce. Toss to coat.
Transfer to a serving bowl or ladle the mac and cheese with prawns and asparagus into individual pasta bowls and serve at once.
Mac and cheese... with prawns and asparagus printed from for personal use only. Not for republication nor distribution.