Preheat oven to 350 degrees F and coat a 9×13 baking dish with cooking spray. Set aside.
In a large saucepan, bring water to a boil. Add pasta and cook 3 minutes shy of until al dente. Drain, rinse and add the cooked pasta to the prepared dish in a single layer.
16 oz elbow macaroni
Evenly sprinkle the chopped cauliflower over the top. Mix together slightly.
2 cups cauliflower
In a large skillet or Dutch oven, melt the butter over medium heat. Add flour and whisk until smooth. Add milk and whisk until mixture is creamy and thickened, approximately 3 minutes.
4 tbsp butter, 1/4 cup all-purpose flour, 3 cups milk
Add white cheddar cheese, sour cream, salt, pepper and paprika to the pan and stir until cheese has melted.
2 cups white cheddar cheese, 1/2 cup sour cream, 1/2 tsp salt, 1/2 tsp pepper, 1/2 tsp paprika
Pour the cheese mixture over the top of the pasta and cauliflower. Top with Parmesan cheese.
1/2 cup Parmesan cheese
Bake uncovered in the preheated oven for 20 minutes or until very lightly golden brown around the edges. Serve immediately!