1) Steam or boil broccolini for no more than 2 minutes. Drain and plunge into ice-cold water to stop the cooking and seal color; drain again. Cut stems into 1/2 inch chunks, stopping before broccolini tops. Slice red bell pepper and scallions.
2) Heat a wok or large, deep skillet over high heat. Add half the oil and then immediately add half the garlic and ginger (use all oil, garlic, and ginger if substituting chicken with vegetables). Cook for 15 seconds, stirring. Add the broccolini, red peppers, white portion only of scallions and diced red chili (optional). Cook over high heat until the broccoli browns and becomes tender but not at all mushy, about 3 to 5 minutes.
3) Turn the heat to medium and remove the vegetables. Add the remaining oil to the pan, then the remaining garlic and ginger. Stir, then add the chicken. Raise the heat to high, stir the chicken once, then let it sit for 1 minute before stirring again. Cook, stirring occasionally until the chicken has lost its pinkness, 3 to 5 minutes.
4) Return the vegetables to the pan and toss once or twice. Add the oyster sauce, agave or sugar, lime juice, soy sauce, a splash of toasted sesame oil (optional), remaining scallions bottoms and chili sauce (if not using fresh chili), toss again. Add nuts, if desired. Raise the heat to high and cook, stirring and scraping the bottom of the pan, until the liquid is reduced slightly and coats the vegetables.
5) Serve immediately over rice and the next day makes fried rice with the leftovers.
6) *Note: Store ginger in the freezer. Peel with a vegetable peeler and grate with a microplane grater.