Melt margarine over a medium-low heat. Add minced green onions and cook 5 minutes. You just want to sweat the onions to soften them up. You're not looking to brown them.

Remove pan from heat, and whisk in remaining ingredients. Put pan back on the stove and bring mixture to a boil over medium heat. Reduce heat and simmer 45 minutes or until sauce darkens and thickens. Cover sauce, then cool and chill until needed.