Japanese Soba

Combine 4 cups of water and the kombu piece in a medium pot. Heat over medium-low heat. Just before the water boils (when small bubbles begin to form around the edges), remove the kombu. Bring the water to a full boil, then immediately remove from heat. Add the katsuobushi, stirring gently. Let steep for 5 minutes without stirring further. Strain the dashi through a fine-mesh sieve lined with cheesecloth into a clean bowl. Discard the strained solids.

In a separate saucepan, combine 3 cups of the freshly prepared dashi with soy sauce, mirin, and sake (if using). Bring the mixture to a gentle simmer over medium heat for 2-3 minutes. Do not boil vigorously, as this can diminish the delicate flavors. Taste the tsuyu and adjust sweetness or saltiness with a pinch of sugar if desired. Keep warm if serving hot, or let cool to room temperature if serving cold.

Bring a large pot (about 8-10 cups) of unsalted water to a rolling boil. Add the soba noodles and cook according to package directions, typically 3-5 minutes. Stir gently during cooking to prevent the noodles from sticking together. Soba cooks quickly, so be careful not to overcook them.

Immediately drain the cooked soba noodles in a colander. Rinse them thoroughly under cold running water, gently rubbing the noodles with your hands to remove excess starch. This step is crucial for preventing stickiness and achieving the perfect texture, especially if serving cold. Drain the noodles very well.

**For Hot Soba (Kake Soba):** Divide the warm, drained noodles into serving bowls. Ladle the hot tsuyu over the noodles. Garnish generously with sliced green onions, and add shredded nori, kamaboko, or tempura if desired. Serve immediately. **For Cold Soba (Zaru Soba):** Arrange the well-drained, cold noodles neatly on a bamboo mat (zaru) or a chilled plate. Serve with a small bowl of cold tsuyu for dipping. Offer sliced green onions and a pinch of shichimi togarashi on the side to be added to the dipping sauce. Shredded nori can be sprinkled over the noodles, and tempura served alongside.