Peel and cube the potato into 1/2 inch diameter pieces; put the potatoes into a pot with about 4 cups of water to cover and boil until fork tender (not quite soft enough to mash). Drain and set aside.
In the same pot on medium heat, cook the ground beef and lightly sprinkle with salt and pepper. Break into serving sized pieces (whatever size you want).
Add the chili powder, if using, to the beef and stir.
When the beef is browned, turn off the heat. Slowly add the flour to the beef in order to make a roux. Mix the flour into the beef completely until no dry flour remains.
Add the green chiles, corn, salt, black pepper and chili powder. Fully mix all the ingredients and place the stockpot back on the stovetop.
Bring up to temperature on medium heat, stirring occasionally. This may take up to 30 minutes or more.
Serve, garnishing with sour cream and cheese if desired.