It takes a little time, but I like to "stuff" my meat (hehe). I don't actually stuff them, I just make 2 patties and press the edges together around bleu cheese and bacon or cheddar and bacon or roasted garlic and grilled onions or whatever. Then I dust the burger with a little kosher salt and ground pepper and grill away. I do like to mix a little garlic powder and onion powder in sometimes. My butcher will grind top round and chuck together for me to get a 12% or so fat content burger which I like, just enough fat to keep them juicy but lots of beef flavor. Nice to have a real old fashioned butcher shop 2 blocks away. Grain and grass fed, no steroids or antibiotics.
