In a small bowl, whisk together the brown sugar, soy sauce, rice vinegar, chili oil, hoisin, sesame oil, minced garlic, ground Szechuan peppercorn, powdered ginger, and salt until well-combined.
Next, add the vegetable broth and chicken broth to a saucepan. Then add the sauce you just mixed, and stir to combine.
Cook soup over medium high heat until just boiling, about 10 minutes, then lower to a simmer (medium to medium-low heat) and cook until reduced by about one third, stirring occasionally. This should take about 30 to 40 minutes.
Serve soup immediately over steamed pork dumplings and top with sliced scallions.