Preheat the oven to 450°F (230°C).
Bring a large pot of salted water to a boil. Add the elbow macaroni and cook until just tender; do not overcook. Drain in a colander and run cool water over the pasta to stop cooking and prevent sticking.
In a large pot or saucepan over medium heat, melt the butter. Whisk in the flour, salt, and black pepper to form a thick paste (roux) and cook 1 minute while whisking.
Slowly whisk in the milk, about 1/4 cup at a time, until smooth. Continue to cook over medium heat, whisking frequently, until the sauce thickens and just begins to bubble around the edges; do not let it boil.
Remove the sauce from heat and whisk in the shredded cheddar until melted and smooth. Stir in the Greek yogurt until fully combined.
Toss the drained macaroni into the cheese sauce, stirring until all pasta is evenly coated. Transfer the macaroni and cheese to a greased 2-qt gratin or 8x8 baking dish, spreading into an even layer.
Combine the breadcrumbs and smoked paprika, then sprinkle evenly over the top of the pasta.
Bake in the preheated oven for 15 minutes, until the topping is golden brown and the dish is heated through. Serve hot.
Optional: for a spicy twist, substitute cayenne pepper for the black pepper.