Line a 12-cup muffin tin with paper liners. In a medium bowl, combine the crushed Biscoff biscuit crumbs with the melted butter. Stir until the mixture resembles wet sand. Divide the mixture evenly among the 12 liners and press down firmly with the back of a spoon or a small glass to create a flat, even base. Place the tin in the refrigerator to chill while you prepare the filling.

In a large mixing bowl, beat the softened cream cheese, Biscoff spread, and powdered sugar together using an electric hand mixer. Continue mixing on medium speed until the texture is completely smooth and no lumps remain. Stir in the alcohol-free vanilla until well incorporated.

In a separate chilled bowl, whip the cold heavy cream until stiff peaks form. Be careful not to overbeat it, as you want a light and airy texture. If you are using agar-agar for extra stability, gently fold the dissolved mixture into the cream now.

Gently fold the whipped cream into the Biscoff cream cheese mixture using a spatula. Use a slow, circular motion to keep the air in the filling. Once combined, spoon the mixture over the chilled biscuit bases. Smooth the tops with a small spatula or the back of a spoon.

Place the muffin tin back into the refrigerator. Allow the cheesecakes to set for at least 4 hours, though leaving them overnight is even better for the best texture. This patience is key to ensuring they hold their shape when removed from the liners.

Once set, carefully remove the cheesecakes from the tin and peel off the paper liners. Melt a tablespoon of Biscoff spread in the microwave for 10 seconds and drizzle it over the tops. Add a small piece of Biscoff biscuit or a sprinkle of crumbs for a final festive touch.