1In 12-inch skillet, cook beef over medium-high heat 5 to 7 minutes, stirring frequently, until brown; drain.
2Stir seasoning mix, water, uncooked pasta, corn, beans and tomato into beef. Heat to boiling; stir. Reduce heat to medium-low. Cover; cook 10 to 15 minutes, stirring occasionally, until pasta is desired doneness and most of the liquid has been absorbed.
3Stir in sour cream. Remove from heat. Sprinkle with cheese and chives. Cover; let stand 2 to 3 minutes or until cheese is melted.