Brown beef and onion in oil in a Dutch oven. Add tomatoes, including liquid, mushrooms, hot water, salt, pepper and sugar. Heat to boiling; reduce heat; cover and simmer until beef is tender, about 1-1/2 hours.
Add marjoram, thyme, potatoes, celery and carrots. Cover and simmer an additional 30 minutes until vegetables are tender. Mix cold water and flour until smooth; gradually stir into beef mixture. Heat to boiling, stirring constantly for 1 minute then remove from heat. Mix Insta-Bake, butter and sour cream until well blended. Drop by spoonful onto hot stew mixture and bake in preheated 450°F oven 10 minutes or until biscuits have browned.
Note: If you don’t have a large oven-safe pot or dutch oven, you may cook the stew on the stovetop, transfer to a 9x13-inch pan, and add biscuit dumplings and bake as directed.