Heat a large pot of water to boiling, add a liberal amount of salt when boiling and add pasta. Cook to just al dente, according to package directions.
Drain and return to pan or crock pot if you want to keep it hot for a while (you don't want to cook it in the crock pot but it can stay on low for a short while, if you plan to leave it in the crock pot for an extended time, you'll want to cook your pasta just shy of al dente so it doesn't turn mushy.).
Meanwhile, melt butter in a saucepan over medium heat. Add flour and whisk to make a roux. Continue whisking until the roux start to turn golden and bubbles, about two minutes.
Add milk and beer, stirring constantly. Cook for about five minutes until the mixture begins to thicken slightly.
Reduce heat to low and add cheeses by the handful, stirring to melt and incorporate. The sauce will thicken slightly but will not be as thick as regular mac and cheese at this point.
Add paprika, mustard, thyme, and salt and pepper to taste.
Pour sauce over pasta and stir to distribute.
Chiffonade basil leaves by stacking and rolling tightly, then use a sharp knife to cut thin slices to form ribbons. Stir basil into pasta and serve.