Cook the pasta. Prepare the elbow macaroni following the package instructions, but aim to cook it for 1-2 minutes less than the recommended time to maintain a slightly al dente texture. Rinse under cold water, then drain and set it aside.
Add pasta to crock pot. In a 4-6 quart crockpot, blend the cooked macaroni, half and half, and cubed butter thoroughly. Ensure an even mixture.
Add cheese. Stir in the shredded medium cheddar, sharp cheddar, mozzarella, and Parmesan cheese into the crockpot. Blend until the cheeses evenly disperse throughout the macaroni and milk.
Seasonings. Introduce the Dijon mustard, garlic powder, onion powder, smoked paprika, cayenne pepper, salt, and pepper. Adjust the spices to suit your taste preferences.
Cook on low. Cover the crockpot with its lid and set it to cook on low heat for 2-3 hours. Stir the mixture every 30 minutes during this period to ensure the cheese melts uniformly and the pasta cooks properly.
Keep an eye on it. Check the consistency after 2 hours of cooking. Should the mac and cheese seem too dry, incorporate a splash of milk and stir. Conversely, if it appears excessively liquid, extend the cooking time for another 30 minutes with the lid partially open to allow moisture to evaporate.
Serve. Once the macaroni reaches tenderness and the cheese sauce achieves a creamy, fully melted state, the dish is ready to serve.