Heat the popcorn chicken according to package directions until very crisp (oven or air fryer both work). Keep it hot on a sheet pan while you make the sauce.
In a small bowl, whisk together the soy sauce, brown sugar, 1 tablespoon plus 1 teaspoon rice vinegar, and orange zest until the sugar looks mostly dissolved. In a separate cup, stir the cornstarch into the cold chicken broth until smooth.
Place a large skillet over medium heat and add the neutral oil. When shimmering, add the green onion whites, garlic, ginger, and chili paste. Cook, stirring, until fragrant and lightly sizzling, 45–60 seconds; do not brown.
Pour in the soy mixture and bring to a gentle simmer over medium-low heat. Let it bubble for 2 minutes, scraping the pan so the aromatics mingle evenly with the sauce.
Whisk the slurry again and stream it into the skillet while stirring constantly. Simmer until the sauce is glossy and thick enough to coat a spoon, 45–60 seconds. Turn off the heat and stir in the sesame oil for a fresh, nutty finish.
Add the hot popcorn chicken to the skillet and toss quickly to coat without lingering on the heat (this keeps it crisp). Scatter over the green onion tops and sesame seeds. Serve at once with steamed rice.