In a medium bowl, combine 2 teaspoons of the vanilla, heavy cream, and condensed milk. Taste and, if you want to boost the flavor a touch, add more vanilla, ¼ tsp at a time; the amount required depends on the vanilla and your palate. An extra pinch of salt sometimes helps too.
With an electric handheld mixer fitted with two beaters or a whisk attachment, whip the mixture at highspeed for about 3 minutes, until you get a firm, spreadable texture like fluffy whipped cream or frosting.
Use a spatula to gently fold in the Teddy Grahams.
Transfer the mixture to a 3 to 4 cup storage container or small, individual containers.
Gently warm the Biscoff in the microwave for 10 to 15 seconds, until it reaches a molasses-like consistency. Drizzle the warmed Biscoff over the cream mixture, then use a chopstick or spoon to create a delicate swirl pattern.
Cover and freeze until firm, approximately 5 to 6 hours, or up to 2 weeks.
Before serving, let the ice cream sit at room temperature for 10 to 15 minutes to soften to a scoopable consistency.
