Prepare the Base - Line an 8×8" loose base or push-up tin with grease proof/parchment paper, ensuring the paper extends up the sides. Arrange a complete layer of Biscoff cookies on the bottom, logo face down. Break or cut cookies as needed to create an even layer that covers the entire base.
Make the Ice Cream Filling - In a medium mixing bowl, combine the dairy-free whipping cream, vegan condensed milk, and Biscoff spread. Using an electric hand whisk or stand mixer with balloon attachment, whip the mixture on high speed for 3-5 minutes until thick and able to hold a peak.
Add the Filling - Carefully pour the whipped cream mixture over the cookie layer, taking care not to disturb the arranged cookies. Use an offset spatula or the back of a spoon to spread the filling evenly, ensuring it reaches all corners of the tin. Gently tap the tin on your work surface to eliminate any air bubbles.
Top Layer - Create a second layer of Biscoff cookies on top of the cream filling. Ensure these cookies align with the base cookies to create perfect sandwich portions when cut.
Freeze Until Set - Place the tin in the freezer and allow the dessert to freeze completely, preferably overnight but a minimum of 6 hours is required for proper setting.
Slice and Serve - Once firmly set, remove from the freezer and lift the entire slab out using the parchment paper overhangs. With a sharp knife, cut into individual sandwich bars along the cookie lines and serve immediately.