In a sauté pan, cook the onions in 2 Tbsp. vegan butter, 2 tsp. salt, and 2 tablespoons of water over medium heat for about 30 minutes (until caramelized with a honey-like color), stirring frequently. Then roughly chop into medium dice-size pieces and add to large mixing bowl.
Meanwhile, in medium-sized pot – cover frozen butterbeans with water, add bay leaf, black pepper, and 2 tablespoons of vegan butter. Bring to boil and cook until completely tender (about 30 minutes). Once done cooking, turn off heat and add 2 tsp. salt and let sit for at least 10 minutes. Then drain beans and add to large mixing bowl.
Using a potato masher – Mash until mixture is about ½ whole beans and half mashed beans. Add chopped onions, spices, and Worcestershire sauce to beans and give a good mix. Then add rice and oats to bean mixture and mix until fully combined. Then, using an ice cream scoop – make patties and place them on a tray lined with parchment paper. Move the tray to the refrigerator and let rest for about 20 minutes. (These can also be frozen and saved for a later date.)
In a nonstick pan – heat grape seed oil over medium-high heat until smoking, then add as many patties as the pan can hold without being crowded. Let burger cook until caramelized and crispy, then carefully flip and repeat on other side. You really only want to flip them once because they may fall apart if you flip too many times.