Put a medium sauce pan of water on high. Peel potatoes and cut into chunks about the size of grapes. When the water boils, add potatoes and simmer over medium-high until cooked through. This will take 20-25 minutes.
While potatoes cook, heat a large cast iron skillet on medium high. Add the hamburger, turn down to medium and stir occasionally until beef is browned.
Preheat the oven to 350 F.
Add the can of chili beans (include all sauce in can) to the beef. Drain the other can of beans and rinse with water. Add to the beef.
When the potatoes are fork tender drain them well. Add potatoes and pepper to the beef mixture. Stir gently to combine. Spread to make an even layer in the skillet.
Top with cheese and bake in preheated oven until casserole is hot through and cheese is melted and bubbly, about 15 minutes.
Check to make sure the center is hot. If you are using a thermometer, it should read 160F.