Instructions

Chop onion, mushrooms and garlic into a very fine brunoise. Leave the slices of bread soaking in milk for about 20 minutes, so that they absorb as much milk as possible. Heat a dash of olive oil in a Magefesa delicia skillet. Cook onion and pepper with a pinch of salt over medium-low heat until the onion is transparent and soft. Let cool for a few minutes. Drain bread.   Place beef and Iberian pork in an kitchen robot. Use the grinding plate with the smallest holes to enable fine chopping. Place freshly minced lamb, poached onion and mushrooms and bread in the bowl of the food processor. Season with salt and pepper, add cumin and chopped mint leaves. Mix on low speed with the dough hook attachment on.
Once ingredients are fully incorporated, divide meat into 4 to 8 portions, depending on the desired size of the hamburgers. Shape each portion into a ball using your hands. Flatten balls into approximately ½ inch thick patties, or the thickness of your taste, taking into account that meat tends to shrink and increase its thickness when placed on the heat. Place burgers on the grill and cook to the desired point of doneness of your guests. Serve garnishing ingredients on the side so that your guests can assemble theirs burgers with the toppings of their preferences.
Never flatten your patties with the back of a spatula to speed up the cooking process. This will make the meat release its juices, resulting in drier, less flavorful burgers.