For the mini burger patties:
- Place a pan over high heat and let it get very hot.
- Coarsely chop the onion and thinly slice the garlic.
- Add 2 tablespoons of olive oil to the pan along with the onion, garlic, salt and pepper.
- Sauté and add the sugar to caramelize them a little.
- When the onion softens and turns light golden, remove from heat and set aside.
- Chop the sandwich bread into pieces and add them to a food processor along with the parsley, mint, sautéed onion mixture, bouillon cube, smoked paprika and thyme. Beat just until the mixture breaks down into breadcrumbs and the ingredients are combined. Do not overbeat or else the mixture will become like a dough.
- In a large bowl, add the bread mixture, ground beef, 5 tablespoons olive oil, egg, salt and pepper. Mix thoroughly with your hands.
- Place a grill pan over medium heat, let it get hot and add 2 tablespoons of olive oil.
- Shape the ground meat mixture into 80 g patties. Add them to the pan and cook for about 3 minutes on each side. You can also cook them for 12 minutes in the oven (preheated to 200*-220* C – 392*-428* F – Fan).
- Add the cheese at the end and let it melt.
- When ready, remove from heat and serve.
For the sauce:
- Combine all of the ingredients for the sauce in a bowl and set mixture aside until needed.
For the burgers:
- Slice the mushrooms and chop the pepper into 2x2 cm cubes.
- Place a pan over very high heat, add the vegetables and sauté until they turn golden and lose most of their liquid.
- Remove from pan and set aside.
- Cut the hamburger buns in half and toast them lightly in the pan, cut side down.
- To assemble each burger, place the bottom part of the hamburger bun on a serving plate, top with lettuce and spread sauce over it.
- Add the burger patty, onion rounds and mushroom mixture.
- Cover with top part of bun and serve.