Consider pulsing a few dried mushrooms in your blender to create a powder. Add this to the mixture when you add the spices to get a deeper flavor without adding any mushroom moisture.
To serve:
You can also shape and size the burgers to be sliders. They hold together better as a smaller patty. Buy a pack of potato slider buns.
Find it online: http://shiftycrafty.com/smoky-black-bean-beet-burgers/