Preheat the oven to 350 degrees Fahenheit. Grease and flour a 15x19x1 inch baking pan or a 13x9 inch pan.
In a large bowl, combine 1 (16.5-ounce) box devil's food cake mix, 1 (21-ounce) cherry pie filling, 3 large beaten eggs, and 1 teaspoon vanilla extract. Pour the batter into the prepared pan.
Bake for 25-30 minutes or until a toothpick inserted in the center comes out clean. Remove from oven and let cool.
In a small saucepan, combine 1 cup granulated sugar, ⅓ cup milk, and 5 tablespoons unsalted butter
Bring the mixture to a boil for about 1 minute and remove from heat.
Stir in 6 ounces chocolate chips until melted and smooth. Pour over the sheet cake and spread evenly over