Step 1

Bring dashi, soy sauce, mirin, and sugar to gentle boil over medium heat. Remove from heat and allow to cool.

Step 2

Set out 4 serving plates. Divide equally among plates: dab of wasabi, grated daikon, and scallions.

Step 3

In the meantime, bring 2-quart pot of water to boil over high heat and add soba. Return water to boil and cook the noodles until tender but firm, 3 to 5 minutes. Have ready a large bowl or pot ready with ice water. Use strainer to remove soba from pot. Place soba into ice water and chill until noodles are cold. Drain noodles.

Step 4

Make mound with noodles on each plate. Pour dipping sauce into individual little bowls to serve alongside noodles.

Step 5

To eat, stir some daikon, wasabi, and green onion into dipping sauce. Take some noodles with chopsticks and dip.