In a large mixing bowl, whisk together the instant vanilla pudding mix and cold milk until smooth and thickened.
Add creamy peanut butter to the pudding mixture and stir until well combined.
Fold in Whipped Topping:
Gently fold the thawed whipped topping into the peanut butter pudding mixture until evenly incorporated. Set aside.
Layer Graham Crackers:
Line the bottom of a 9×13-inch baking dish with a single layer of graham crackers, breaking them as needed to fit.
Spread Peanut Butter Mixture:
Spoon half of the peanut butter pudding mixture over the layer of graham crackers and spread it out evenly with a spatula.
Repeat Layers:
Add another layer of graham crackers on top of the peanut butter mixture, followed by the remaining peanut butter pudding mixture. Smooth the top with a spatula.
Prepare Chocolate Topping:
In a microwave-safe bowl, combine chocolate chips, butter, milk, and vanilla extract.
Microwave in 30-second intervals, stirring in between, until the chocolate is melted and smooth.
Top with Chocolate:
Pour the melted chocolate mixture over the top layer of the peanut butter pudding mixture, spreading it out evenly with a spatula.
Chill:
Cover the baking dish with plastic wrap and refrigerate the Peanut Butter Eclair Cake for at least 4 hours or overnight to allow the layers to set.
Serve:
Once chilled, slice the cake into squares and serve cold.
