To remove some of the bitterness you can steam the tempeh for 20 to 30 minutes before using it. If you are gonna bake these burgers in the oven you should preheat the oven to 200 celcius or 400 Farenheit.
Drain the beans and place them in a big bowl and mash them
Process the oats, flax seed, nutritional yeast and spices until everything is ground up.
After you've removed the dry mixture from the food processor add the onion, steamed tempeh, corn, garlic and herbs and pulse until everything is chopped. Now add everything to the bowl of beans and mix well
Form patties out of the mixture and bake them in the oven for 25 to 30 minutes, flipping them halfway through. To cook them in a pan you can add a little bit of oil and panfry them on medium heat for 4 to 5 minutes on each side.