Line a 7x7 square pan or dish with baking paper, leaving extra hanging over the edges so you can lift the frozen slab out later.
Add the whipping cream, condensed milk, and strawberry puree into a bowl and whisk on high for about 3-4 minutes, until the mixture is thick and holds soft peaks.
Gently twist or slide a butter knife between the top and bottom halves of each biscuit sandwich to separate them cleanly.
Arrange the bottom biscuit halves cream-side up across the base of the pan in a single layer (about 16 biscuits if using JimJams). Spread the strawberry ice cream evenly over the top with an offset spatula.
Add spoonfuls of strawberry jam over the ice cream and swirl gently with a knife or offset spatula.
Finish with the top biscuit halves, cream-side down, matching them up with the bottoms below.
Wrap the pan tightly in cling film and freeze for 6-8 hours (or overnight, for best results). Once set, slice along the biscuit lines and serve immediately.