Combine crushed Biscoff cookies with melted butter until evenly moistened. Press lightly into the bottom of the serving dish.
Beat the cream cheese until smooth, then add sweetened condensed milk and vanilla extract. Mix until creamy and lump-free.
In a separate bowl, whisk the instant pudding mix with cold milk until thickened (about 2 minutes). Fold this into the cream mixture.
Whip the heavy cream to soft peaks and fold gently into the filling for a mousse-like texture.
Spread half the filling over the cookie base, add crushed Biscoff cookies, and top with the remaining filling.
Drizzle melted Biscoff spread or caramel sauce in thin lines. Swirl lightly with a knife for a marbled effect.
Garnish with whole or halved Biscoff cookies, then cover and refrigerate for at least 4 hours or overnight.
