Using a food processor, pulse 4-5 chunks of the frozen short ribs at a time until ground (being careful not to over-process the meat and so you can still see a coarse texture).
Place the ground meat in a large bowl and continue until you've ground all the short ribs.
Add the Italian sausage (casings removed) in with the ground short ribs and the minced garlic.
Add the salt and pepper.
Use hands to mix the meat until just combined being careful not to over mix the meat which will cause tough burgers.
Use a 1/2 cup measure to scoop out some ground meat and form into patties.
Place each patty onto a parchment-lined baking sheet that has been sprayed lightly with cooking oil.
Continue forming patties until all the meat has been formed into patties. *Note - If you're making a lot of burgers, place parchment paper between the layers of burgers so they don't stick together.
Refrigerate until you're ready to grill.
30 minutes before you're ready to grill remove the patties from the fridge and allow them to come to room temperature.
Season the patties again with additional salt and pepper. *Note - Before you place the patties on the grill press your thumb into the center of each patty so you see the indentation. This will keep your burgers flat as they cook and will prevent them from having a dome top.
Cook the burgers over medium-high heat (flipping once) until they reach your desired doneness.
Add a cheddar cheese slice to each burger at the final moment of cooking and remove the burgers from the grill. Cover to keep warm.
Place each burger on a pretzel roll (I suggest grilling those for a minute or two also) and add the toppings and condiments of your choice...but don't forget the BACON!!!