Cook 16 ounces of pasta in a large pot of salted boiling water according to package directions until al dente. Drain and set aside.
While the pasta cooks, add 1 pound of lean ground beef to a large skillet over medium-high heat. Break it up as it cooks. Once fully cooked through, drain any excess grease and return the meat to the skillet.
Add 8 ounces of cream cheese, 8 ounces of shredded sharp cheddar cheese, 1/2 teaspoon garlic powder, 1 teaspoon salt, and 1/2 teaspoon onion powder to the skillet. Stir continuously until both cheeses are fully melted and no lumps remain.
Pour in 1 cup of milk slowly, stirring constantly as you add it, until the sauce is smooth and evenly combined.
Add the cooked, drained pasta to the skillet and stir until every piece is coated in the cheese sauce. Serve immediately.