Chuck will give you about 80/20 lean/fat ratio, which is ideal for a burger. You can do a mix of brisket and short rib if you like, but I'd experiment with that another time. Make sure your meat is very cold (if it's a little stiff because it's slightly frozen, that is fine), and grind it once. You will need to mix it by hand a little so the patties stay together, but not too much that they become tough. This will take practice and getting a feel for it. I like to go with 6 ounce patties, because you can leave them a little thicker and cook them to medium since you're grinding your own meat and there's less bacterial contamination that you have to worry about. Once you have the patties formed, put a quarter-sized dimple in the top of the patty to ensure it stays flat when you cook it. Season generously with salt, and cook them on a screaming hot cast iron pan or flat top. As soon as they're done, hit them with some very finely ground black pepper.