Black Bean Meatless Balls (Vegan, Gluten-Free, Oil-Free)

½ medium yellow onion

garlic

sliced white mushrooms

½ cup walnuts*

(425g) can black beans, rinsed and drained thoroughly

flax egg (combine 1 tbsp ground flax + 2.5 tbsp water)

¾ cup bread crumbs**

fresh basil, optional

tamari

½ tsp salt, plus more to taste

smoked paprika

chili powder

jar marinara sauce