In a saucepan, heat 2 Tablespoons of toasted sesame oil to medium-high heat. Add scallion, ginger, and garlic. Stir fry on medium until garlic begins to brown around the edges.
Increase heat to high and stir in Soy Sauce, Vinegar and water and bring to a boil.
Add dark brown sugar and stir until sugar is dissolved.
Lower heat to low and cook for 20 minutes, stirring often. Remove from heat, cover, and allow to steep for 2 hours.
Refrigerate overnight.
When ready to serve, strain into a serving container, add fresh minced scallion, chili oil, white vinegar, chili paste, and chinese mustard. Stir to combine. Taste and adjust seasonings.