Melt the butter in a large cast-iron skillet over medium-high. Add the beef, black pepper and 1/2 teaspoon of salt. Cook, stirring to crumble, until browned, about 5 minutes.
Preheat the broiler with the oven rack 3 to 4 inches from the heat. Reduce the stovetop heat to medium, and stir in the macaroni. Add the milk, warm water, dry mustard, paprika, garlic powder, cayenne pepper and remaining 1/2 teaspoon salt. Bring to a low simmer and cover; reduce the heat to low. Cook, stirring occasionally, until the macaroni is tender and cheeses melt. Stir in the chives and jalapeños (if using).
Excerpt from Valerie’s Home Cooking by Valerie Bertinelli. Copyright © 2017 by Valerie Bertinelli. Used with permission by Oxmoor House. All rights reserved.