01 - Preheat oven to 375°F. Grease a 9x13-inch baking dish.
02 - Boil macaroni in a large pot of salted water until just al dente, about 7 minutes. Drain and set aside.
03 - Melt unsalted butter in a medium saucepan over medium heat. Whisk in flour and cook, stirring, for 1 to 2 minutes until bubbly but not browned.
04 - Gradually whisk in whole milk until smooth. Stir in Dijon mustard, garlic powder, onion powder, smoked paprika, salt, and black pepper. Cook, whisking constantly, until thickened, about 5 minutes.
05 - Remove saucepan from heat. Stir in shredded sharp cheddar and Monterey Jack until melted and smooth. Adjust seasoning as needed.
06 - Mix drained macaroni with cheese sauce, ensuring even coating. Transfer mixture to the greased baking dish.
07 - In a mixing bowl, combine panko breadcrumbs, finely chopped dill pickles, melted unsalted butter, fresh dill, and crushed red pepper flakes until evenly combined.
08 - Evenly distribute the pickle crumble topping over the macaroni and cheese in the baking dish.
09 - Bake on the center rack, uncovered, for 20 to 25 minutes, until the topping is golden brown and the casserole is bubbling.
10 - Allow to rest for 5 minutes before serving.