Make-ahead tip: The dish can be prepared up to a day in advance. Prepare and cool casserole. Cover and refrigerate overnight. Let stand on counter for 40 minutes before baking. Bake dish as directed or until the temperature near the center reaches 165°F.
Flecked with chopped chilies, pepper jack is a blend of mild monterey jack cheese with, typically, green and red jalapeño peppers. The peppers give the cheese a spicy kick, and the level of heat varies by the brand.