Skillet Creamy Mac and Cheese

From Mel. Rob loves this stuff because it's more flavorful than my old recipe--I used to just make a white sauce and add cheese, this is much better. It's super quick. If I have 15 minutes, I'll make this over Kraft any day. I make it in my lodge cast iron skillet.

INGREDIENTS

• 3 1/2 cups water, plus extra if needed
• 1 (12-ounce) can evaporated milk
• 12 ounces (about 3 cups) elbow macaroni (I weigh it, 12 oz is  usually less than 3 cups. I like it creamier anyway)
• 1/2 teaspoon salt
• 1 to 1 1/2 teaspoon cornstarch
• 1/2 teaspoon dry mustard
• 1/4 teaspoon hot sauce (I've never added this, but I should...)
• 6 ounces cheddar cheese, shredded (1 1/2 cups) (when i weigh it, it's closer to 2 cups shredded)
• 6 ounces Monterey Jack cheese, shredded (1 1/2 cups) (when i weigh it, it's closer to 2 cups shredded)
• 2 tablespoons butter, cut into small chunks 
• Ground black pepper to taste

1. 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. (I go less, we like it al dente)
2. 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.
3. 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.