Crush the walnuts and miso together to form a chunky paste. Use a mortar & pestle if you have one.
In a medium pan, heat a drizzle of olive oil over medium heat. Add the shallots and let them cook down for about one minute.
Add the mushrooms, tamari, garlic powder, onion powder and five-spice powder and stir. Cook until the mushrooms are cooked down, 5 to 8 minutes.
Add a splash of mirin to deglaze the pan, then add in the walnut/miso paste mixture and drizzle with the honey. Stir everything together then remove from the heat and transfer to a medium bowl.
Set it aside to cool for several minutes before adding the egg.
Stir in the egg and ¼ cup of the panko, and let the mixture chill in the fridge for 15 minutes.
Meanwhile, combine the remaining ¼ cup of panko and the sesame seeds on a shallow plate.
Remove the mixture from fridge and form into 6 small 3-inch patties.
Lay each patty in the breadcrumbs, then spoon more over the tops to cover. Use your hands to firmly press them into shape. It’s ok if they fall apart a little, but if they're falling apart too much, let the patties firm up in the fridge for another 10 minutes before you cook them.
Wipe out the pan you were using before and drizzle in a few tablespoons of olive oil over medium heat. Cook the patties for 2 to 3 minutes per side.
Serve on buns with desired toppings.