To make the caramelized onions, place a frying pan on medium heat then add the oil. Once hot, add the onions. Reduce heat to low and sauté onions for 15 minutes. Once they are nice and tender, add in the balsamic vinegar and brown sugar then further caramelize for roughly 20 minutes.
In a bowl, add the two cans of black beans. With a potato masher or fork, squish the beans until the have partially broken up (leave some whole pieces for substance). Next add the rest of the burger ingredients to the bowl. Stir to combine combine and then set aside for 15 minutes.
It’s time to make the blue cheese sauce. Blend together all the ingredients for the sauce until smooth and creamy.
Back to patties. Divide mixture into patties and then fry in batches on medium heat in a saucepan until brown on each side and cooked through.
Preheat oven for the buns to be browned. Put buns in the oven.
Serve patties on toasted buns with lettuce, avo, onion and cheesy saucy (or, in this case, serve on top of the perishable content in your bin).
May they RIP (sadly not in my stomach).