Miso Lentil Burgers with Caramelized Onions

Steps

1. Cook the lentils: bring the lentils and 600 g of the water to a boil in a skillet with a lid, then simmer covered for 20 to 25 minutes until tender. Drain well and spread out to cool for 10 minutes.
2. Make the patty mix: in a bowl, mash the kidney beans with a fork, leaving some pieces. Add the cooled lentils, oats, egg, garlic, paprika, soy sauce, salt and black pepper and mix until the mixture holds together.
3. Shape the mix into 4 patties about 1/2 inch thick and chill them on a plate for 15 minutes so they firm up.
4. Meanwhile, start the topping: wipe out the skillet, heat one third of the olive oil over medium heat, and cook the onion for 15 minutes, stirring often, until soft and golden.
5. Add the mushrooms to the onion and cook 6 to 8 minutes until browned.
6. Make the miso glaze: in a small bowl, whisk the miso paste into the remaining 20 g of water until smooth.
7. Pour the miso glaze over the mushrooms and onions and stir for 1 minute until glossy. Transfer the topping to a bowl and wipe out the skillet.
8. Heat half of the remaining olive oil in the skillet over medium heat. Cook 2 patties for 4 to 5 minutes per side until crisp and heated through to 160°F (71°C) in the center, since they contain egg. Repeat with the last half of the olive oil and the other 2 patties.
9. Build the burgers: lay the spinach on 4 slices of toasted bread, add a patty, pile on the miso mushrooms and onions, and top with the remaining 4 slices of toasted bread.