In a medium bowl that allows room for whisking, whisk peanut butter to loosen it. Add each ingredient one at a time, whisking thoroughly after each addition. (You are making an emulsion, and adding the liquids slowly in batches prevents a sloshy mess from forming. It will actually go faster this way, and will minimize cleanup.)
Whisk in warm water, one tablespoon at a time, until the sauce thickly drips from the whisk. You want the sauce to be thin enough to easily coat the nooks and crannies of the vegetables and noodles, but to retain some body. Depending on the thickness of your peanut butter and the room temperature, you will add between 1 Tablespoon and ¼ cup of water. Taste and make any adjustments of sweetener, lime juice, spicy heat, or perhaps salt. Set the peanut sauce aside.
Place a pot of salted water on to boil. Cook soba noodles according to package directions. When done, rinse in cold water until the noodles are completely cold.
While the water is heating and the noodles are cooking, prep your vegetables including the green onions. Aim for small dice, or thin matchstick pieces so that you can fork up a mix of vegetables and noodles in each bite. Place all the vegetables in a large bowl..
Coarsely chop the cilantro and peanuts. Keep a few tablespoons of each aside for garnish, and place the rest in the bowl. When the noodles are cooked, rinsed, and drained, add them to the bowl. Give everything a gentle toss.
Add about ½ cup of the peanut sauce to the bowl, and give everything a gentle but thorough toss, until all ingredients are evenly coated with peanut sauce. Add more sauce, tablespoon by tablespoon, until the salad is dressed to your liking.
Plate the salad individually or transfer it to a serving bowl or platter. Sprinkle cilantro, peanuts, and sesame seed on top. Serve with a lime wedge.
Refrigerate any leftovers in an airtight container. Will keep nicely for a day.