In a medium bowl, combine the graham cracker crumbs and melted butter. Mix well until the crumbs are evenly coated.
2 cups graham cracker crumbs, ½ cup unsalted butter, melted
Press the graham cracker mixture into the bottom of a 9x13-inch baking pan to form the crust. Use the back of a spoon or a flat-bottomed measuring cup to press it down firmly.
In a large bowl, whisk together the chocolate pudding mix and 4 cups of cold milk until the mixture thickens. Let it sit for a few minutes to fully set.
2 3.9 ounce boxes instant chocolate pudding mix, 4 cups cold milk
Pour the chocolate pudding over the graham cracker crust in an even layer.
Arrange the sliced bananas over the chocolate pudding.
4 ripe bananas, sliced
In another large bowl, whisk together the banana pudding mix and 3 cups of cold milk until it thickens. Let it sit for a few minutes to set.
2 3.4 ounce boxes instant banana pudding mix
Pour the banana pudding over the sliced bananas in an even layer.
Spread the Cool Whip over the top of the banana pudding layer, making sure to cover it completely.
1 8 ounce container Cool Whip, thawed
Optionally, garnish the top with chocolate shavings or a dusting of cocoa powder.
Chocolate shavings or cocoa powder for garnish (optional)
Refrigerate the pudding bars for at least 2 hours, or until set.
Once set, cut into squares or bars and serve chilled.