In 12-inch nonstick skillet, cook sausage and mushrooms over medium-high heat 5 to 7 minutes, stirring frequently, until no longer pink. Add 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 12 minutes, stirring occasionally, until pasta is tender and sauce is thick. Remove from heat.