Preheat broiler. Mix together peanut butter, water, sesame oil, soy sauce, sambal oelek, and rice vinegar. Toss chicken thighs and Broccolini in sauce, and place on a rimmed baking sheet. Broil 10 inches from heat until chicken is cooked through, about 10 minutes (watch to make sure it doesn't burn).
Took Amy H's advice and thinned it out a little bit. Also made it a spicier, for our taste. Served with sliced cucumbers since the sauce was satay like. DELICIOUS.
I just made this. I used broccoli instead of broccolini, and doubled the sauce because I doubled the chicken. The sauce is ok, but it needs something, like fish sauce. If I make this again, I would thin out the sauce a little more, add a couple of teaspoons of fish sauce and maybe some sugar. Good idea, definitely needs some tweaking.