This is not so much a recipe, but more of a list of suggestions. There are several ways to stuff a cheeseburger. It basically depends on what you want to stuff it with. Small burgers can be stuffed with small items such as shredded cheese, finely diced mushrooms and veggies. This is easily done by taking a ball of meat, about 1/4 pound and forming it into a cup then filling it up with your chosen fillings then folding the edges in to seal it back up into a ball and then pressing it flat. I choose to go for the larger stuffed burgers. This takes a lot more time but it is well worth it. This method involves pressing 2 thin patties out on wax paper, about 1/4 pound per patty then putting the filling between the patties and crimping the patties together with a fork to seal the edges. The small burgers can be cooked easily anywhere, use smaller diced ingredients and add cheese on top. The larger burgers are better cooked in a skillet or if grilling outdoors invest in a burger cage for the ease of turning, with the larger burgers use larger sliced ingredients and put the cheese inside if you wish.
Here is a list of me and my family's favorite fillings...