|Start with the beans and rice first. If you have dried black beans, prepare those first. If you have frozen black beans, thaw and mash. Canned black beans are fine. Put black beans into a bowl. If you have frozen, cooked rice, thaw. Otherwise, prepare and set aside to cool.
Pre-heat oven to 350 degrees. Peel and chop the sweet potatoes, dropping them into cold water as you cut them. Drain well and toss with 1 tsp olive oil and salt. Spread them out in an even layer on a lightly oiled baking sheet. Roast in the oven for 25-30 minutes, or until tender. Toss occasionally.
While sweet potatoes roast, heat 1 tsp olive oil in a large pan over medium high heat. Add the onion and garlic and cook til lightly browned.
Add onion & garlic to bowl of mashed black beans. Stir in the tamari (or soy sauce), cumin, and salt & pepper, to taste.
Add the cooked rice and sweet potatoes, Worcestershire sauce, and 1 oz of cornmeal. Mix well and adjust the seasoning.
Form into (10) 4 1/2 oz patties, then dredge lightly in remaining cornmeal.
Heat a cast iron skillet over medium high heat and add 1-2 tsp olive oil. Add the burgers and brown lightly on each side. Place on baking sheet and bake for 10 minute, to heat thoroughly.
Serve on hamburger buns with lettuce, tomato, and sliced avocado.