We like brown rice pasta here for three reasons: It’s whole-grain, it’s a dead ringer (taste- and texture-wise) for traditional pasta, and it’s gluten- free. You could also use a wheat- or chickpea-based pasta.
Stir together milk, 2 cups water, and salt in a Dutch oven; bring to a boil over high. Stir in pasta. Reduce heat to medium-low; simmer, stirring often and gently to loosen pasta from bottom of pot, until just tender, about 12 minutes. (Do not over-stir, or pasta may become mushy.)
Remove from heat. Add cheeses and pepper; stir gently until melted. Sprinkle with additional pepper.