- Cook penne according to package directions, omitting salt; drain.
- Sauté mushrooms in hot oil over medium heat in Dutch oven or large saucepan 1 minute; remove.
- Melt butter in same pan. Add flour, garlic and basil; cook, stirring, until smooth. Gradually stir in milk and cook until thickened and bubbly. Cook, stirring, 1 minute longer. Stir in 1 cup cheese until melted. Remove from heat and stir in soy sauce.
- Add mushrooms, spinach and penne, stirring until all ingredients are evenly coated with sauce. Turn out mixture into greased 9×13-inch baking pan; sprinkle evenly with remaining 1 cup cheese.
- Bake in 350ºF. oven 20 minutes, or until heated through.