Preheat oven to 375ºF. Grease and flour a 15 ½ x 10 ½ x 1'' jelly-roll pan. In a medium bowl, combine margarine and sugar. Add eggs one at a time, mixing well after each. Stir in chocolate syrup until well-combined. Add flour, vanilla, and salt and mix well. Pour into pan and spread evenly. Bake 15-20 minutes. To make the frosting, heat milk in a small saucepan over medium-high heat for three to five minutes, being careful not to let it scorch. Add sugar and stir until dissolved. Break butter into sections and add to mixture. Bring to a boil and cook for one minute, stirring constantly. Add chocolate chips and continue to stir until completely melted. Pour over cake. Frosting will harden as it cools.
