How to Make It
In a bowl, combine the ground meats, mixing gently with your hands. Divide the meat into 4 pieces and gently shape each into a 3/4-inch-thick patty. Set the burgers on a baking sheet, cover with plastic wrap and refrigerate until firm, at least 2 hours.
In a small bowl, whisk the ground coriander with the ancho powder, cumin, smoked paprika, oregano and chipotle powder to combine.
Light a grill or preheat a grill pan. Generously season the burgers on both sides with salt. Grill over high heat until browned on the bottom, about 3 minutes. Flip and top each burger with 1 teaspoon of the spice blend; reserve the remaining spice blend for another use. Continue grilling the burgers until browned outside and medium-rare within. Transfer the burgers to a rack, top each with 2 ounces of the crumbled queso fresco and let rest for 3 minutes. Spread the toasted buns with the crema. Set the burgers on the buns, top with the avocado, red onion slices and cilantro leaves and serve.
Ground skirt steak can replace the ground brisket, the ground short rib or both.