Cook soba noodles (9 oz or so), drain, rinse. Plunge into hot water to reheat.
For broth, combine 5 cups dashi stock, 1/3 cup shoyu, 1 tablespoon sake, 1 tablespoon sugar and heat. Pour over noodles. Garnish with chopped green onions. Add other stuff like shrimp tempura, green bean tempura, etc, on top.