Cook pasta according to package directions in a Dutch oven.
Drain, reserving ¼ cup of the pasta water.
In the same pan, melt the butter and cook until bubbly. Add the flour and start stirring to form paste. Let this cook for a couple of minutes until it starts to turn golden. Watch it close, don't let it burn.
Alternate adding the milk, beer, and pasta water. Let the sauce bubble for a couple of minutes to temper the alcohol flavor.
When smooth and creamy stir in the shredded cheeses and chile powder. Add the cooked macaroni and stir until blended. Taste and adjust flavors for saltiness.
Notes
Tips for Success:
Cheese can carry a lot of salt. Once you've finished stirring the macaroni into the cheese sauce, taste before adding salt to season.
Letting the cheese sauce bubble for a couple of minutes will temper the alcohol flavor in the beer.
Pasta noodles will continue to soak up some liquid once they sit. Drizzle on a little milk to thin once they've been stored.