Step 1

Bring a large pot of salted water to a boil. Add the cauliflower and boil until the cauliflower is fork tender, 8 to 10 minutes. Drain and place the cauliflower in a blender. Add the Parmesan cheese, olive oil, garlic, mustard, butter, lemon juice, salt, and several grinds of pepper.

Step 2

Cook the pasta in a large pot of salted boiling water according to package directions or until al dente. Drain the pasta, reserving 1½ cups of the starchy pasta water. Add 1 cup of the pasta water to the blender and blend the sauce until creamy.

Step 3

Transfer the pasta to a large bowl or skillet. Add the sauce and toss to coat. If the sauce is too thick, add the remaining ½ cup pasta water and toss again to loosen the sauce and make it a bit creamier.

Step 4

Sprinkle with parsley and season to taste. Serve with grated cheese on the side.