Step 1

Sauté vegetables: Heat 1 tablespoon grapeseed oil in a skillet over medium-high heat. Add onion, sauté until golden at the edges, about 5 minutes. Add mushrooms and cook until onions have browned and mushrooms have released their moisture, about 5 minutes. Transfer to a food processor.

Step 2

Start mixing burgers: To the food processor, add pepitas, tomato paste, chipotle peppers and adobo sauce, cumin, and salt. Pulse until nearly smooth (there should be no full pumpkin seeds left), scraping down the sides a couple times to incorporate.

Step 3

Finish mixing burgers: Add black beans and pulse until they’re mostly pureed (some bits are fine, for texture). Add cooked rice and pulse until evenly distributed. Transfer mixture to a large bowl. Use a rubber spatula to fold in breadcrumbs.

Step 4

Form patties: Divide the mixture into 6 tightly packed balls (approximately ¾ cup each). Use your hands to flatten and shape each ball into burger patties (no more than 1-inch / 2.5 cm thick).

Step 5

Grill patties (see note 3): Preheat a grill over medium. Brush patties generously on both sides with oil (to prevent sticking). Grill, covered, until browned on the outside and firm to the touch, about 5 minutes on each side.

Step 6

Make Chipotle Mayo: Meanwhile, whisk together mayo and adobo sauce. Taste and add more adobo sauce if you'd like.

Step 7

Assemble: Spoon chipotle mayo onto burger buns. Add a burger patty and and toppings of your choice (quick pickled red onions, avocado, lettuce, tomatoes).