From Richard Blais' cookbook Try This at Home, this burger recipe exemplifies his creative thought process in the kitchen. Onions are candied in sherry vinegar for a truly unique take on caramelized onions, and bacon and Cheddar are the cherry on top of this burger sundae.
Melt the butter in a large saucepan over medium-low heat. Add the onions, garlic, and thyme leaves and stir. Cover and cook, stirring frequently, until the onions are deep golden brown, about 45-60 minutes.
Add the sugar, salt, and pepper and stir. Replace the lid and cook for 10 minutes more.
Add the vinegar and scrape up any browned pits in the pan, mixing it into the onions. Cook until the liquid has evaporated, about 10 minutes. Transfer to a container and let cool completely, then cover and refrigerate for up to 2 weeks.
Form the meat into 4 patties, about ¾-inch thick, and, with the handle of a wooden spoon, make an indentation in the middle of each patty. Season the patties on both sides, using 1 ½ teaspoon of salt and ½ teaspoon of pepper for each one.
Heat 2 tablespoons of the olive oil in a large cast-iron skillet over high heat until smoking. Place the beef patties in the pan, immediately reduce the heat to medium-high, and cook for 4 minutes; do not press on the burgers so they retain their juices. With a spatula, flip the patties and add the butter, garlic cloves, and thyme to the pan. Once the butter has melted, tip the pan and baste each burger a few times, spooning the hot butter over it. Continue to cook, basting often, until the burgers are well browned on the bottom and the meat is medium-rare, 5-6 minutes. Remove the burgers from the hot pan, top each with a slice of Cheddar, and let rest for 5 minutes.
To build the burgers, put 2 slices of tomato on each muffin bottom, followed by a burger. Top each with 2-3 tablespoons candied onions, some bacon, and the top bun. Serve immediately.