Step 1Trim and peel the daikon radish, then cut it crosswise into 3-inch pieces. Julienne the pieces, then place the julienned strips into a large bowl, and toss in the onion and snow peas.
Step 2In a medium bowl, whisk together the sesame oil, rice vinegar, sugar and salt. Pour half of the dressing over the slaw and toss to coat. Add more dressing as needed, a couple of tablespoons at a time, until the slaw is lightly coated and flavorful; you may not need all of the dressing. This makes about 8 cups slaw.
Step 3Cover and refrigerate the slaw for at least 1 hour for the flavors to develop. Before serving, toss with the black sesame seeds. The slaw will keep for 1 day, refrigerated.