01 - Preheat oven to 200 degrees Celsius (400 degrees Fahrenheit). Lightly grease a 23x33 cm (9x13 inch) baking dish.
02 - Cook pasta in generously salted boiling water until just al dente. Drain thoroughly and set aside.
03 - In a skillet, heat olive oil over medium heat. Season diced chicken with salt, black pepper, and garlic powder. Cook until the chicken is golden brown and cooked through, approximately 5-7 minutes. Remove from skillet and set aside.
04 - In a saucepan, melt butter over medium heat. Whisk in flour and cook for 1 minute, stirring constantly to form a smooth paste.
05 - Gradually whisk in milk into the saucepan. Continue cooking and whisking until the sauce thickens to a smooth consistency, about 3-5 minutes.
06 - Remove the saucepan from heat. Stir in shredded cheddar cheese, shredded mozzarella cheese, Dijon mustard, paprika, and dill. Season generously with salt and pepper to taste.
07 - In a large mixing bowl, combine the cooked pasta, sautéed chicken, prepared sauce, and chopped dill pickles. Mix until all ingredients are evenly coated.
08 - Pour the pasta mixture into the prepared baking dish and spread evenly.
09 - In a separate bowl, combine the crushed pickle chips, panko breadcrumbs, and melted butter. Mix thoroughly.
10 - Sprinkle the crust mixture evenly over the surface of the pasta bake.
11 - Bake in the preheated oven for 20-25 minutes, or until the topping is golden brown and the casserole is bubbling around the edges.
12 - Allow the casserole to rest for 5 minutes before serving. Garnish with additional fresh dill, if desired.