Preheat oven to 350°F. Brown beef in a large skillet.
When beef is cooked, remove from heat, drain, and set aside.
Using the same skillet, combine water and onion soup mix, covering to cook for 5 minutes.
Whisk flour and milk together in a small bowl. Then, add to skillet.
Cook this mixture until a nice gravy forms.
Add cooked beef and veggies, if desired, stirring to combine thoroughly.
Spray a casserole dish with nonstick cooking spray and pour beef mixture into dish.
Spread potatoes into a layer on top of the beef mixture.
Bake in over on 350°F for about 20 minutes.
Sprinkle with cheddar cheese and return to oven just until cheese is melted.