Blend the sauce base: Add the cottage cheese, milk, Dijon mustard, cornstarch, and black pepper to a blender. Blend until completely smooth.

Sear the beef: Heat olive oil in a large skillet over medium-high heat. Add the steak in an even layer and cook quickly until browned but not tough. Remove to a plate.

Cook the vegetables: In the same skillet, add onion, bell pepper, and mushrooms if using. Cook for 6 to 8 minutes until softened and lightly golden.

Add seasoning: Stir in garlic, Worcestershire sauce, smoked paprika, and salt. Cook for 30 seconds until fragrant.

Build the sauce: Lower the heat to medium-low. Pour in the blended cottage cheese mixture and stir until warm and slightly thickened. Add cream cheese if using and stir until smooth.

Melt in the cheese: Add provolone and cheddar a handful at a time, stirring after each addition so the sauce stays creamy.

Adjust the texture: If the sauce feels too thick, add a splash of reserved pasta water until glossy and spoon-coating.

Combine everything: Add the cooked pasta and beef back to the skillet. Toss gently until coated and warmed through.

Serve: Taste, adjust salt and pepper, and serve hot with extra black pepper or provolone if desired.