Add tofu, peanut butter, misugaru, matcha powder, salt, sugar, and milk to a blender.
Don't cut back on the sugar! it'll taste too bitter. If you're worried about sugar, swap in a sugar substitute or honey instead.
Blend on high until completely smooth with no lumps. Refrigerate the broth while you prep everything else.
Boil the egg and cut it in half. Julienne the cucumber thinly. Halved cherry tomatoes on top are a nice touch for color too.
Cook buckwheat noodles. Drain and rinse thoroughly under cold running water. Rub between hands to remove starch. This is what makes the noodles chewy.
Add the noodles to a bowl and pour the chilled matcha soy broth generously over them. Top with egg, julienned cucumber, and tomato (optional), add ice, and eat right away.