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.