Step 1

Preheat oven to 350 degrees F. Coat a 9- x 13-inch baking dish with cooking spray. Add batter and bake according to package directions; let cool.

Step 2

Using the end of a wooden spoon, poke holes about 1-inch apart all over top of cake.

Step 3

In a medium bowl, whisk pudding mix and milk until slightly thickened. Pour mixture into holes and spread evenly over top of cake. Chill 1 hour.

Step 4

To make Chocolate Glaze, in a medium saucepan over low heat, combine sugar, cornstarch, water, and chocolate; cook until chocolate is melted and mixture is thick and smooth, stirring constantly.

Step 5

Remove from heat and stir in vanilla. Allow to cool, then spread gently over top of cake. Chill 2 hours or until ready to serve.