Place pasta in a large pot and cover with water. Salt generously (add enough salt so that you are slightly disgusted with yourself) and bring to a boil, stirring to prevent the pasta from sticking. Cook for around 6-7 minutes - pasta should be shy of al dente.
Reserve 200ml or so of pasta water and drain pasta before putting back into pot. Add evaporated milk, stir to combine, and bring to a boil. Add cheese, stir to combine, and then add 'nduja and stir.
Reduce heat to low and cook, stirring until the cheese has melted and the 'nduja is fully incorporated into the pasta. The liquid should reduce to a creamy sauce - if the cheese hasn't melted, keep stirring. If the sauce looks too thick, add some reserved pasta water. Taste for seasoning and serve.