caramelize the onions (or at least cook them soft) in a pan and set aside.
Mix ground beef with salt and pepper and form into 4 patties, grill to desired doneness.
In the meantime, shred the cheese so it will melt better and slice the brioche buns and spread butter on each side, grill until lightly browned (you can also use just two buns if you want to do open faced sandwiches).
Place cooked patties on the grilled buns. Add the shredded cheese then hot fries to each burger and pour on a generous helping of gravy and top with caramelized onions. Serve hot.