Preheat the oven to 350 degrees F.
Wash, peel and thinly slice the potatoes. Place them in a large, microwavable bowl and cover them with cold water. Microwave them on high power for 10 minutes. Drain the potatoes.
Meanwhile, brown the ground beef in a skillet and drain the fat if necessary.
Open the cans of green beans and drain one of the cans.
Pour the green beans and the liquid from one can into a large, clean bowl.
Add the cream of mushroom soup, Worcestershire sauce, onion flakes and pepper. Mix until well combined.
Stir in the drained potatoes and the browned ground beef until evenly mixed together.
Evenly spread the hamburger and potato mixture into a casserole dish.
Cover the dish with foil.
Bake at 350 degrees for one hour.
Take the casserole dish out of the oven and discard the foil.
Top the casserole with the cubes of Velveeta cheese.
Increase the heat of the oven to 450 degrees F and bake, uncovered, for an additional 15 minutes, or until the cheese is bubbly and starting to brown.