Grate all three cheeses straight from the block — pre-shredded is coated and refuses to melt smooth. Mix them, and set HALF aside for the layers.
Boil the cavatappi in salted water just short of al dente. It finishes cooking in the oven; mushy spirals are a tragedy.
Melt the butter with half the seasonings, whisk in the flour, and let the roux bubble for a minute or two.
Pour in the evaporated milk a little at a time, whisking. When it thickens, add the cream, the rest of the seasonings, and the dijon.
Melt the cheese into the sauce one handful at a time — patience here is what makes it silky instead of grainy. Fold in the pasta.
Layer it: half the mac, a snowfall of reserved cheese, the rest of the mac, more cheese on top. Bake at 350°F for 25–30 minutes until bubbly, then broil 2 minutes for the golden crust.
The moment: crack the crust with a spoon and lift slow. The pull tells you everything.
midnight tip — block cheese or nothing. the anti-caking dust on pre-shredded is why sauces go grainy.