In a large bowl, combine the instant vanilla pudding mix and cold milk. Beat them both with a whisk until they become smooth. Let the mixture set at room temperature for 5 minutes to thicken.

Add the sweetened condensed milk and vanilla extract into the pudding mixture and stir.

Gently fold in the whipped topping (e.g., Cool Whip) until it's well combined with the pudding mixture.

Spread a thin layer of pudding onto the bottom of your casserole dish and place a single layer of cookies over it.

Add a layer of banana slices on top of the cookies.

Pour 1/2 of the remaining pudding mixture over the bananas and wafers. Spread it evenly.

Repeat the layers with the remaining Nilla wafers, bananas, and the rest of the pudding mixture.

Add a final layer of bananas and crushed Nilla wafers on top.

Cover the baking dish with plastic wrap and then place it in the fridge for at least 6 hours, or preferably overnight.

Before serving this delicious banana pudding, feel free to garnish the top with whipped topping and a few Nilla wafer crumbs.