The origin of the hamburger is disputed though "hamburger steak sandwiches" have been advertised in U.S. newspapers from New York to Hawaii since at least the 1890s.
Just like sandwiches, a good burger relies on 3 equally important things: the bread, the patty and condiments. My first choice for the bun goes for Pretzel bun, challah bread and then pain de mie/pullman sandwich bread. Due to its high fat content, brioche should be the least choice for burgers.
To make the juiciest, most flavorful burgers, ground meat ratio is 70 percent lean and 30 percent fat. For healthful burgers, 80/20 are still pretty juicy and tasty.
Bring vinegar, sugar, garlic and herbs to a boil. Turn off the heat and add onion slices. Let cool and keep pickled onions refrigerated for weeks.
Mince ginger and shallots. Sweat shallots in fat for 5 minutes on medium heat. Add some fresh thyme is desired. Add ginger and ground black pepper and continue to cook for a few more minutes until fragrant. Transfer shallot mixture to a plate and cool then reserve in the refrigerator (do not add hot shallots to the ground meat). Use an 1/8" hole grinder plate to grind meat. Add the chilled shallot-ginger mixture and the eggs*. Make 12 burger patties and refrigerate.
*Adding egg to hamburger meat can help hold the meat together for easier cooking. Without the proper binder, the burgers may fall apart in the pan or on the grill.
Remove gorgonzola cheese rind, and work it out at room temp to soften. Make twelve 1.5 ounce/40g disks. Keep refrigerate or freeze for later use.
Heat 2 frying pans; one to toast the bun and the other to sear the meat. Slice and toast bread and reserve on the cutting board (avoid spreading mayo over hot bread). Meanwhile, season burger patty with salt. Add a drizzle of grape seed oil in the hot pan and sear the meat 3 minutes on medium-high heat. By the time it cooks, spread mayo on the bread, add lettuce and tomato. Then flip the meat, wait one minute and add the chilled gorgonzola disk. Cook for 2 minutes more until internal temperature reaches 135ºF/57ºC for medium-rare. After 3 minutes cooking, give a quick sear to the cheese by flipping over burger for a few seconds. Flip patty back and baste it with melted cheese and rendered juice left in the pan – finish the burger, enjoy!