Cook the pasta. Bring a large pot of salted water to a boil. Cook the pasta until just shy of al dente (1 minute less than the box suggests).
Drain, reserving 1/2 cup of the starchy pasta water.
Blend the protein base. In a blender, add cottage cheese, Greek yogurt, milk, Dijon, garlic powder, onion powder, and paprika. Blend until completely smooth and silky, about 30–45 seconds.
Temper the whey. If using protein powder, whisk it in a small bowl with 2–3 tablespoons warm pasta water to make a smooth slurry. This prevents clumping and keeps the sauce from getting grainy.
Warm the sauce gently. In a large pot over low heat, add butter and cream cheese.
Stir until just melted. Pour in the blended mixture and the whey slurry. Warm gently, stirring, until steamy but not boiling.
Melt in the cheese. Add cheddar a handful at a time, stirring between additions until melted and smooth.
Stir in Parmesan. If it gets too thick, loosen with a splash of pasta water or milk.
Season. Taste and add salt and pepper. Sharp cheddar is salty, so season at the end for the best control.
Combine with pasta. Add the drained pasta to the pot and toss to coat.
Let it sit on low heat for 1–2 minutes so the pasta finishes cooking and absorbs the sauce.
Adjust texture. If the sauce tightens, add small splashes of warm pasta water until it’s creamy and glossy.
Serve hot. Plate it up and finish with extra black pepper or a pinch of paprika if you like.