In a large mixing bowl, whisk together the instant vanilla pudding mix and cold milk until smooth and thickened, about 2 minutes. Add the sweetened condensed milk and whisk again until fully combined.

Gently fold in the whipped topping with a spatula until the mixture is creamy and airy.

In a large trifle dish or 9×13-inch glass pan, begin layering the dessert: Layer 1: A base of vanilla wafers; Layer 2: Sliced bananas; Layer 3: Sliced strawberries; Layer 4: A generous spoonful of pudding mixture. Repeat the layers until you run out of ingredients, ending with a layer of pudding on top.

Cover the dish with plastic wrap and refrigerate for at least 4 hours—or overnight if you have the time.

Before serving, top with extra whipped topping, fresh strawberry slices, or banana coins if desired. Serve cold.