Preheat oven to 375 degrees F (190 degrees C). Grease 2 baking sheets. Whisk together 2 cups sugar and the cinnamon, reserve.

Beat together 1 cup sugar, margarine, eggs, milk, flour, and baking powder in a large bowl to form a dough. Divide dough into 10 balls. Spread the prepared cinnamon and sugar mixture onto work surface. Use a rolling pin to roll each dough ball out on the cinnamon sugar, forming each into a 14 inch circle. Cut each circle into 8 wedges. Roll each wedge into a crescent, starting at the wide side and rolling toward the tip. Place rolls on prepared baking sheets.

Bake crescents in preheated oven until set and lightly browned, about 20 minutes.

While crescents are baking, mix together 2 cups sugar, vanilla, 2 cups water, and the cornstarch in a saucepan. Bring to a boil, and cook until thick. Brush glaze on baked crescent rolls. Allow glaze to set for 5 minutes. Drizzle melted chocolate over glazed crescents. If desired, serve warm.