In a large bowl, whisk together the sweetened condensed milk, instant vanilla pudding mix, and cold water. Mix until smooth and thickened. Stir in the melted Biscoff cookie butter until fully combined. The mixture should be creamy and well blended.
In a separate bowl, whip the cold heavy cream using a mixer until stiff peaks form. This step creates a light and airy texture that balances the rich pudding base.
Gently fold the whipped cream into the pudding mixture. Use a spatula and mix slowly to keep the texture fluffy. Continue folding until no streaks remain.
Spread one-third of the pudding mixture into the bottom of your dish. Add a layer of Biscoff cookies and sliced bananas. Repeat the layers until ingredients are used, finishing with pudding on top.
Cover the dish and refrigerate for at least 3–4 hours. This allows the cookies to soften slightly and the flavors to blend beautifully.
Before serving, top with crushed Biscoff cookies, banana slices, or a drizzle of melted cookie butter for extra flavor and presentation.