Heat the oil in a medium saucepan. Add the onion and cook over moderate heat, stirring, until browned, about 10 minutes. Add the garlic and cook for 2 minutes, then add the bourbon and simmer for 2 minutes longer. Stir in the vinegar, sugar, chipotle chiles, mustard, ancho chile powder, bay leaf and allspice and bring to a boil. Cover and cook over low heat for 30 minutes.