i made twice the amount of onions and mushrooms and used the other half to top the burgers. sauté them in a little oil with a sprinkle of salt and garlic powder till they're soft.
in the mean time mash the beans and mix with the egg, cheese, and spices.
let the mushroom mix cool a little so it doesn't immediately cook your egg then stir into the bean mix.
add bread crumbs a bit at a time until you have a nice solid mixture you can shape easily.
shape into 8 patties (not 6 big ones, trust me), and chill in the freezer for 15 min.
fry in a little oil on med-low heat until nice and brown. i topped mine with swiss cheese, cooked mushrooms, fresh spinach, and aioli on a ciabatta bun. yum! i think the texture might be better with mashed red lentils, we'll have to try that. i think any kind of bean would work fine for this (except maybe garbanzos since they have more of a fish texture when mashed). i have the rest of these still in my freezer as cheep, healthy, easy standby food.