Boil the pasta like it says on the packet. The twisty ones (fusili) work well.
Meanwhile, throw the bacon and musrooms into a non-stick frying pan and keep it moving for ten minutes or so.
When the pasta is done, drain it. While it's still hot, put the pesto in the pot and stir it all around so that it coats the pasta.
Send the bacon and mushrooms into the pot and mix it up some more.
Decant it into a couple of bowls. Give one to the Stepson.
Have a Cadbury's Curly Wurly for pudding.