Preheat the oven to 350 degrees F.
Combine the Biscoff crumbs, brown sugar, and melted butter in a bowl. Press a heaping tablespoon of the mixture into the bottoms of the cavities of a mini cheesecake pan. (Or use a muffin tin lined with cupcakes liners)
In the bowl of a stand mixer fitted with the paddle attachment (or using a hand mixer) combine the cream cheese and sugar on medium-high speed until smooth (about 1 minute)
Add the sour cream, eggs and vanilla, and beat on medium speed until smooth and well-combined.
Fill each cavity of the pan to the brim, smoothing down the tops with a spoon.
Bake the cheesecakes for about 15-18 minutes, until the sides are set. Take out immediately if the tops begin to crack.
Allow the cheesecakes to cool in the pan for about 20 minutes, then unmold and cool completely on a plate. Chill in an airtight container for at least 2 hours, and preferably overnight.
For the mango coulis: peel and chop on mango and puree the flesh with a hand blender, or full-size blender until smooth. Add juice one tablespoon at a time and blend until desired consistency is reached.
Top the cooled cheesecakes before serving with coulis and a mint leaf if desired.