01 - In a large mixing bowl, beat the heavy cream with an electric mixer on medium-high speed until stiff peaks form, approximately 2 to 3 minutes.
02 - Gently fold the sweetened condensed milk, vanilla extract, and melted Biscoff spread into the whipped cream using a spatula. Work carefully to maintain the airy texture until the mixture is smooth and uniform.
03 - Line a 9x5-inch loaf pan with parchment paper and pour the ice cream mixture into it. Smooth the surface evenly with a spatula, then cover and freeze for at least 4 hours or until completely firm.
04 - Remove the ice cream from the freezer and let it rest at room temperature for about 5 minutes to soften slightly for easier scooping.
05 - Place 8 Biscoff cookies flat side up on a parchment-lined baking sheet. Using an ice cream scoop, place approximately 1/4 cup of ice cream onto each cookie. Top each with a second cookie and press down gently to form an even sandwich.
06 - If desired, roll the edges of each sandwich in crushed Biscoff cookies to coat. Return the assembled sandwiches to the freezer for 10 to 15 minutes to firm up before serving.