In 12-inch nonstick skillet, cook beef, onion and garlic over medium-high heat 5 to 7 minutes, stirring frequently, until some pink remains. Stir in mushrooms and green beans; continue cooking until beef is no longer pink. Add milk, hot water and sauce mix (from Hamburger Helper™ box); stir to combine. Stir in uncooked pasta (from Hamburger Helper™ box). Heat to boiling, stirring occasionally. Reduce heat; cover and simmer about 10 minutes, stirring occasionally, until pasta is tender and sauce is thick.