Add the mushrooms in the bowl of the foodprocessor and pulse until finely ground. Place into a large bowl. Add tofy and the waterchestnuts to the processor and ground them finely.
Add the tofu mixture, tahini, egg, garlic, salt, pepper and 2/3 of the buck wheat flakes to the mushrooms and mix with your hands until it forms a coherent mixture. Shape into 4 buns
Place the remaining buckwheat flakes on a flat plate and press the burgers carefully in it until covered on all sides. Heat the oil in a pan on medium heat. Bake each burger for about 3-4 minutes each side or until golden.
Serve the burgers with cucumber ribbons and a spicy mayonaise or sauce of your liking.