Bring a large pot of salted water to a boil and cook the elbow macaroni according to the package instructions until al dente.
Drain the cooked macaroni and set it aside.
In a medium saucepan, melt the butter over medium heat.
Add the flour to the melted butter and whisk continuously for 1-2 minutes to form a roux.
Gradually pour in the milk while whisking constantly, ensuring there are no lumps. Add the dry mustard, salt, and black pepper to the saucepan, and continue whisking until the mixture thickens, approximately 5-7 minutes.
Remove the saucepan from the heat and gradually stir in the shredded cheddar cheese until it melts and the sauce becomes smooth and creamy.
Preheat the oven to 350°F (175°C).In a large mixing bowl, combine the cooked macaroni and the cheese sauce, stirring until the macaroni is evenly coated with the sauce.
Transfer the macaroni and cheese mixture into a greased baking dish.
Place the baking dish in the preheated oven and bake for 15-20 minutes or until the top is golden and bubbling.If desired, sprinkle paprika over the top for added color and flavor.Once baked, remove from the oven and let it cool for a few minutes before serving.
Divide the mustard mac and cheese into individual servings and garnish with a sprinkle of paprika, if desired.This dish pairs well with a simple green salad or steamed vegetables, making it a satisfying and well-rounded meal.