Preheat oven to 350 degrees,
Cook pasta in a large pot of salted boiling water according to package directions. In the last 3 minutes add the cauliflower (The directions on the wholewheat pasta that I used called for a cooking time of 10-12 minutes. The pasta should be al dente, so I cooked it for 7 minutes, added the cauliflower and drained the water off after 10 minutes total).
Drain the pasta and cauliflower and place in a large bowl.
In a small heavy bottomed saucepan melt 3 tbsp of the butter.
Whisk in the flour and cook for 2 minutes.
Add the milk in a slow stream and whisk to combine. Bring the mixture to a boil and then reduce to a simmer. Cook for 3 minutes stirring occasionally .
Add 2 cups of the grated cheese and stir until melted.
Pour the cheese sauce over the pasta and stir to combine.
Place in a buttered baking dish (approximately 11 x 7 inches).
Sprinkle remaining 1/4 cup cheese over the pasta with cheese.
Bake for 30 minutes and serve.
(Can be prepared the night before, refrigerated and baked the next day.)