1poundof elbow macaronicooked and drained, reserve 1/4 cup of pasta water
1/2cupheavy cream or half & half
12roasted Hatch chilestops chopped, some charred skin removed with hand. Don' rinse chiles under water.
2-3medium tomatoescored and chopped
Heat the oven to 350 degrees. Toss the panko bread crumbs with the 1 teaspoon of melted butter on a small baking pan. Toast the bread crumbs until lightly browned, about 7-10 minutes. Set aside to cool. Once cooled, add chopped cilantro.
In a large saucepan, heat the butter over medium heat until melted, then stir in the flour. Stir until the mixture is blended and smooth, about 1-2 minutes.
Remove from the heat and slowly whisk in the milk. Add the dry mustard, white and Chamayo pepper, and salt. Return to heat and stir until mixture begins to boil, then reduce the heat to low and simmer for 30 minutes, stirring occasionally. Stir in the chopped Hatch chiles and tomatoes.
Stir in 5 cups of the cheese until melted. Pour the sauce over the cooked macaroni in a large bowl, stirring until all of the macaroni is coated. If the mixture seems dry or you're not hearing that "perfect pasta sound" add a little of the pasta water for consistency. Pour the macaroni into a well-buttered 9- by 13-inch casserole. Drizzle heavy cream around the edges of the casserole. Sprinkle on it the remaining cheese, then the toasted bread crumbs.
Cover the casserole with aluminum foil. Bake 20 minutes. Remove the foil and bake uncovered an additional 10 minutes. Put under a preheated broiler for 5 minutes.