- Prepare the onions:
Melt the butter in a skillet over medium-low heat. Add the sliced onions and season with salt and pepper. - Caramelize slowly:
Cook the onions for 20–30 minutes, stirring regularly, until they become deeply golden and soft. Add a small splash of beef stock whenever the pan becomes dry. Continue cooking until the onions are rich and caramelized. - Finish the onions:
Pour in the remaining beef stock and simmer for several minutes. Let the liquid reduce until the onions are glossy and intensely flavored. Set aside. - Make the truffle mayo:
Combine mayonnaise, mashed black garlic, truffle oil, lemon juice, and a small pinch of salt. Mix until smooth and creamy. - Form the burgers:
Divide the ground beef into two large portions or four smaller ones. Shape them into patties slightly wider than the buns. Season both sides generously with salt and black pepper. - Cook the patties:
Heat a skillet or griddle over medium-high heat. Add a little butter or oil and cook the patties until browned and cooked to your preferred doneness. - Add the Swiss cheese:
Place a slice of Swiss cheese on each burger during the final minute of cooking. Cover the pan briefly to help the cheese melt completely. - Toast the buns:
Cut the buns in half and toast them cut-side down in the same skillet until golden and lightly crisp. - Assemble the burger:
Spread a generous layer of black garlic truffle mayo over the bottom bun. Place the cheesy beef patty on top, then pile on a generous portion of the caramelized onions. - Finish and serve:
Add the toasted top bun and serve immediately while the Swiss cheese is still warm and gooey and the caramelized onions are rich and savory.
See more on the next page