Heat the oil in a nonreactive saucepan. Add the onion and jalapeño and cook over moderate heat, stirring, until wilted, about 3 minutes. Add the ketchup, vinegar, sugar, mustard and Tabasco and bring to a simmer. Add the blueberries and simmer over low heat, stirring until thickened, about 10 minutes. Yields 1-1/2 cups.