Step 1

In a large mixing bowl, whisk together the milk and instant vanilla pudding until well combined. Set aside to thicken for a few minutes, stirring occasionally. Once thickened, fold in the Cool Whip.

Step 2

Place a single layer of graham crackers in the bottom of a 9x13-inch pan. Top with half of the pudding mixture. Add another single layer of graham crackers, then the remaining pudding mixture. Top with a final layer of graham crackers.

Step 3

Scoop the chocolate frosting into a microwave-safe bowl and heat in 15-second increments until melted, stirring well between each cooking interval. Pour the frosting over top of the eclair cake.

Step 4

Refrigerate the eclair cake for about 30 minutes until the chocolate frosting is set, then cover with plastic wrap and chill overnight, or 8 hours.

Step 5

Slice the eclair cake into 12 servings and serve chilled.