Serve this sweet-sour sauce with chicken, pork loin, or Brandied Ham.
In a medium saucepan, heat oil over medium-high. Add shallots and cook, stirring occasionally, until golden brown at edges, 3 minutes. Add mustard seeds and cook, stirring, until beginning to pop, 1 minute. Add remaining ingredients and 1/2 cup water; bring to a boil. Reduce to a simmer and cook until thickened, about 6 minutes. Let cool to room temperature before serving.
To store, refrigerate, up to 3 weeks.