The pork should help to moisten that up, add flavor and bind the patties. That's why I use ground chuck. That extra lean beef is way too dry for grinding. It's great for tacos, chili, sloppy Joe's, etc.
I will have to try that, If Im mixing it with pork, I just worry about the added fat content that the chuck has.
I never made a burger mixed with pork before, but I sure make meatballs that way and never had a problem with them falling apart. Too many bread crumbs makes things fall apart if there's not enough moisture... Like in crab cakes. If you're making the patty and it won't stay together (if you have a lot of onions or garlic in there) mix in some raw egg. It acts like a binder and keeps things together. By the way, at the cafe I use some pre made patties (8 oz) that are made from ground choice angus chuck. They come in frozen and you're not supposed to thaw them out before cooking because they contain a beef demiglace mixed in with the ground beef. If you thaw them out, they get drier. I cook them over a gas char grill that I have under the hood. The demi glace gives them moisture and even more beef flavor. They're delicious. The brand I use is called TNT and now there are several knock offs. Some are just as good and others not so. I think the difference is the beef demi. I'm sure you can get something like that retail at the better stores like Rouses or WD... meybe even Walmart. I never looked. If you want to try adding a demi to your own recipe I'd try mixing a beef base with some water to make a thick slurry and mix it in with the fresh bround meat. You can probably use beef boullion cubes, but you can get the paste at Sam's. One brand is called "better than Boullion". I once bade a stuffed patty with some leftover smoked pulled pork by making two thin patties and sealing the stuffing in the middle between the two patties. it was ok but I had to be gentle cooking them because I was afraid they'd fall apart when flipping. I like burgers a lot. I'm an American, but I have to admit Dude is right about the Cuban sandwich. they're all good, but the best are Platonic!
On the subject of cheese....has anyone ever tried pepper jack on their burger? Gives it a little extra zip that I don't find is there from cheddar or American.
Excellent choice MC, I think it does add that extra kick. I love provolone or a slice of smoked gouda on a burger as well.