1. Bring two medium saucepans of salted water to a boil. Add the potatoes to one of the pans and cook until tender, about 10 minutes. Remove with a slotted spoon and drain well. Meanwhile, cook the green beans in the other pan until tender, about 4 minutes. Remove with a slotted spoon and drain well. As a pan becomes available, cook the carrots and broccoli, separately, until just tender, about 4 minutes each. Drain the vegetables well.
2. Meanwhile, puree the peanut butter, garlic, red-pepper flakes, brown sugar, lemon juice, soy sauce, salt, and hot water in a blender. Put one of the empty saucepans over moderately low heat. Pour the sauce into the pan and warm through. Stir in the scallions and cilantro.
3. Pour a little sauce on one large platter or individual plates. Arrange all the vegetables in small piles over the sauce. Sprinkle with the seeds or nuts and serve with the remaining sauce.
Wine Recommendation: Riesling and Asian food go together like Romeo and Juliet. Did you know that great rieslings are made in Australia's Clare Valley? Some are now being imported into the U.S., and this would be a great time to try one.