Cook the brown rice as per package instructions if not pre-cooked.

In a skillet over medium heat, toast the walnuts for 5-7 minutes until golden and fragrant. Set aside to cool.

Using the same skillet, add olive oil and diced onion. Sauté with a pinch of salt and pepper until onions are soft and translucent.

In a food processor, combine toasted walnuts, chili powder, cumin, smoked paprika, salt, and pepper. Process until finely ground.

Transfer the mixture to a bowl. Add cooked rice, panko bread crumbs, and barbecue sauce. Mix until well combined.

Form the mixture into four patties, each about 3/4 inch thick.

Preheat a grill or skillet over medium heat. Cook the patties for about 5 minutes on each side or until heated through and crispy on the outside.

Serve the patties on buns with lettuce, tomato slices, and pickles.