2portobello mushroomslarge, stems removed and caps finely chopped (preferably using a food processor)
pepperfreshly ground, to taste
1 1/2cupsbread crumbs
1/2cupyamcooked, mashed - more if needed
6 to 12lettuce leavesif substituting for hamburger buns
3tomato slicesif used
3/4cupguacamoleor avocado - if used
First, rinse the quinoa well. Bring the water to a boil and add the quinoa, cooking until finished, 12 to 15 minutes, careful not to overcook. Drain, measure 2 cups and set aside.
In a large sauté pan, heat the olive oil over low heat and add the shallot and red pepper flakes. Cook until the shallots are soft, about 3 minutes. Add the mushrooms and cook for 3 more minutes to soften, stirring often.
Place the mixture in a large bowl and add the quinoa, then add salt and pepper to taste. Set aside to cool and then add the breadcrumbs and mashed yam, kneading the mixture to fully incorporate and form the burger base. Test the mixture by forming a very small patty and frying it in a sauté pan; if the burger is too soft to hold together, add more mashed yam to bind. Make 8 patties by pressing the mixture firmly with your hands.
Heat a thin layer of olive oil in a large skillet or grill pan over medium heat. Cook the patties until golden-brown on both sides, 3 to 4 minutes per side.
Place the burger on a lettuce leaf (if using) and then top with tomatoes, guacamole or slices of avocado.