Add the instant vanilla pudding mixture and milk to a large bowl. You can mix with an electric mixer or a whisk.
Add the whipped topping. Make sure that the whipped cream is thawed, then fold into the pudding mixture.
Using graham crackers, line the bottom of a 9x13 baking dish. You may have to break some to cover the entire bottom. For estimation purposes, each layer of graham crackers is about one sleeve.
Add half of the pudding mixture. Make sure that you're using just half of pudding mixture and cover the bottom layer of graham crackers. Spread it out smoothly using a spatula.
Add another layer of graham crackers. On top of the pudding mixture you just added, add another graham cracker layer.
Spread the other half of the pudding mixture. Add the remaining pudding mixture on top of this layer of crackers.
Put the final layering of crackers on top of the pudding mixture.
Melt and make the topping. Put the heavy cream, vanilla, and chocolate chips into a microwave-safe bowl and heat up for 1 minute. Stir, then continue heating in 30-second increments. Make sure that you're stirring between each time. Once the mixture is smooth, let it cool down for a few minutes and then pour it over the top of the eclair cake. Smooth it out using a spatula.
Chill in the fridge. Put a cover on the dessert recipe and let it chill for at least 8 hours. Overnight is best if possible.