1/2 cup vegetable oil
1/2 cup white sugar
1 (15 ounce) can boiling water
1 1/2 cups packed light brown sugar
1 tablespoon cornstarch
1 1/2 teaspoons vanilla extract
1 cup brown sugar for decoration
Heat oil in large saucepan over medium heat. Dissolve sugar in water. Bring to a simmer, stirring constantly. Boil for 5 minutes, stirring constantly. Remove from heat; stir in boiling water. Remove from heat and stir chocolate syrup and brown sugar. Bring to a boil, stirring constantly, over medium heat. Boil, stirring constantly, for 5 minutes. Remove from heat and stir in cornstarch. Pour into foil-lined 1-quart foil-lined 9x13-inch dish. Pour chocolate syrup and brown sugar over chocolate fudge. Spoon chocolate syrup over chocolate fudge by molding dough over top. Cover and refrigerate for 30 minutes.
Dissolve vanilla extract in 1/4 cup boiling water in small bowl; add chocolate syrup and chocolate syrup by spoon of spoon. Chill for at least 2 hours; pour fudge over chocolate fudge. Chill until serving. Refrigerate leftover fudge.