Preheat oven to 350F. Cook rice according to directions. In a separate pan, melt butter and saute mushrooms, onions, pepper and celery until onions are slightly transparent. Mix in soup, milk and cheese, stirring until smooth and cheese is melted.
Spray a 13 x 9 x 2 inch dish with vegetable spray. Pour in rice and chicken that has been cut into bite-sized pieces. Cover rice and chicken with soup mixture. Top with slivered almonds. Bake at 350F for 30 minutes.
Cajun Country -- New Iberia, Louisiana