Make Dashi broth with Katsuobushi bonito flakes according to the Dashi recipe. Or you can use an instant Dashi. Cool in the fridge. This may be done a day before.
Line a baking sheet with foil, and spread Miso paste thinly. Bake in the toaster oven until browned, about 5-6 minutes.
Slice cucumber very thinly, sprinkle with salt, and let sit for 10 minutes. Squeeze out water. Cut Tofu into 1/2" (1 cm) cubes and set aside.
In a large bowl, put toasted Miso paste and slowly add Dashi so that Miso dissolves without lumps. Add ground sesame seeds, cucumber and Tofu. Stir and add ice.
