Melt butter in medium saucepan on medium-high heat. Add mushrooms and onion; cook and stir 2 minutes or until onion begins to soften.
Stir in water and Rice Mix. Bring to boil, stirring occasionally. Reduce heat to low; cover and simmer 20 minutes. Stir in cream and cheese; cover and cook 5 minutes longer or until rice is tender. Stir in spinach. Remove from heat. Let stand 5 minutes. Fluff with fork before serving.