Add the ground beef and diced onion to a large skillet over medium-high heat. Cook for 6-8 minutes, crumbling the beef, until fully browned. Add the minced garlic and cook for 1 minute. Drain excess grease.

Add tomato paste, Worcestershire sauce, paprika, garlic powder, mustard powder, salt, and black pepper to the skillet. Stir and cook for 1 minute.

Transfer the seasoned ground beef to a 6-quart slow cooker. Add 2 cups of beef broth and stir to combine.

Cover and cook on low for 2-3 hours or high for 1-2 hours.

Turn the slow cooker to high. Add uncooked elbow macaroni and the remaining 1 cup of beef broth, preferably warmed. Stir and press the pasta into the liquid.

Cover and cook on high for 25-40 minutes, or until the macaroni is tender. Stir after 15-20 minutes and check regularly. Add a little warm broth if the mixture becomes too dry.

Turn off the slow cooker. Stir in the milk and 1½ cups of shredded cheddar cheese until creamy.

Sprinkle the remaining ½ cup of cheddar cheese over the pasta. Cover for 5-10 minutes until melted.

Stir gently, taste, adjust seasonings if needed, and serve immediately.