Remove the stems from the mushrooms and rub off any dirt with a paper towel. Finely chop with a knife and add to a mixing bowl.
To the bowl, add the scallions and garlic. Toss to combine. Add the beans to the bowl and mash them with a fork until most are mashed, but some larger chunks remain. Stir together.
Add the rest of the ingredients (minus the flour) and stir again to combine. Add the flour, 1 tablespoon at a time, stirring between each addition until you get a dough that can be shaped and holds together.
Form the dough into patties and place on a parchment-lined plate or baking sheet. Pop in the fridge and chill for at least 30 minutes, preferably longer.
When ready to cook, heat some oil in a non-stick skillet. Cook the burgers over medium-high heat for 3 - 4 minutes per side, until each side is crispy and dark brown.
Serve on top a toasted Little Northern Bakehouse bun with your desired toppings.
Freeze extra patties and reheat in the toaster oven or on a pan.
* Burgers can also be baked if you'd prefer! Bake on a parchment-lined baking sheet at 375ºF for 30 - 35 minutes, flipping halfway through.** Nutrition facts include bun + toppings.