01 - Pour the cold heavy whipping cream into a large mixing bowl. Using an electric mixer on medium-high speed, beat until stiff peaks form, approximately 2 to 3 minutes. Be careful not to overwhip.
02 - Add the sweetened condensed milk, vanilla extract, and melted Biscoff spread to the whipped cream. Gently fold with a spatula until the mixture is smooth and uniformly combined, preserving as much air as possible.
03 - Line a 9×5-inch loaf pan with parchment paper, leaving overhang on the sides for easy removal. Pour the ice cream base into the pan and smooth the surface with a spatula. Cover tightly and freeze for at least 4 hours or until completely firm.
04 - Remove the ice cream from the freezer and let it sit at room temperature for about 5 minutes to soften slightly, making it easier to scoop and spread.
05 - Arrange 8 Biscoff cookies flat side up on a parchment-lined baking sheet. Scoop approximately 1/4 cup of the softened ice cream onto each cookie. Top each with a second cookie and press down gently to create an even sandwich.
06 - If desired, roll the exposed edges of each ice cream sandwich in the crushed Biscoff cookies to create a decorative and crunchy coating.
07 - Return the assembled sandwiches to the freezer for 10 to 15 minutes to firm up before serving. Store any leftovers wrapped individually in plastic wrap for up to 1 week.