3-1/2 cups water, plus extra if needed
1 (12-ounce) can evaporated milk
12 ounces (about 3 cups) elbow macaroni
1/2 teaspoon salt
1 teaspoon cornstarch
1/2 teaspoon dry mustard
1/4 teaspoon hot sauce
6 ounces cheddar cheese, shredded (1-1/2 cups)
6 ounces Monterey Jack cheese, shredded (1-1/2 cups)
2 tablespoons butter, cut into small chunks
Ground black pepper to taste
Bring 3 1/2 cups water, 1 cup of the evaporated milk, the macaroni, and 1/2 teaspoon salt to a simmer in a 12-inch nonstick skillet over high heat. Cook at a vigorous simmer, stirring often, until the macaroni is tender and the liquid has thickened, 9 to 12 minutes.
Whisk the remaining 1/2 cup evaporated milk, the cornstarch, mustard and hot sauce together in a small bowl, then stir into the skillet. Continue to simmer slightly thickened, about 1 minute.
Off the heat, stir in the cheddar and Monterey Jack, one handful at a time, adding water as needed to adjust the consistency of the sauce (I didn’t need any additional water when I made it). Stir in the butter and season with salt and pepper to taste. Serve immediately.
Ham and Pea Variation: Follow the recipe, adding 4 ounces deli-style baked ham, diced medium, and 1/2 cup frozen peas to the skillet with the cornstarch mixture in step 2.