For this salad, it's important to use Tuscan kale (also called dinosaur or lacinato kale); it's more tender and has a delectable sweetness that's missing from other varieties. Cut out any tough stems and thick central ribs before slicing the kale into very thin strips. It's a sturdy green, so it can stand up to an assertive dressing, like ranch or blue cheese, if you prefer.
Combine the peanut butter, vinegar, tamari, sesame oil, ginger, garlic, sesame seeds, chile sauce, and 1/4 cup of water in a food processor or blender. Purée until smooth, adding more water to thin the dressing if needed.
Place the kale in a large bowl and toss with some of the dressing. Add the scallions, radishes, and orange segments, and toss again to coat. Transfer the salad to a platter and garnish with the peanuts, if desired.