01 - Bring a large pot of salted water to a boil. Add the diced potatoes and cook for 5 minutes. Add the pasta and cook together until both are tender, approximately 8-10 minutes. Drain and set aside.
02 - Meanwhile, melt butter in a large saucepan over medium heat. Whisk in the flour and cook for 1 minute to form a roux.
03 - Gradually whisk in the milk, stirring constantly until smooth and slightly thickened, about 3-4 minutes. Lower the heat, add shredded cheddar, Dijon mustard, garlic powder, and black pepper. Stir until the cheese melts and the sauce is smooth.
04 - Stir in the pickle brine and half of the chopped pickles into the cheese sauce.
05 - Add the drained pasta and potatoes to the sauce, tossing to coat evenly. Serve immediately, garnished with the remaining pickles, sliced green onions, and smoked paprika if desired.