Soak the cashews in boiling water for at least 15 minutes.
Grease a 6 inch spring form (or loose bottom) cake pan (that is at least 3 inches deep) with a little vegan butter or oil. Line the bottom of the pan with a circle of parchment paper (draw around the base of your pan then cut it out), then line the sides too. Greasing first helps to hold it all in place.
Add the cookies and softened or melted butter to a food processor (or blender) and process until completely crushed and combined. You can also bash the cookies up with a rolling pin until fine crumbs, then mix them with melted butter in a bowl.
Press the buttery cookie mixture really tightly into the bottom of the lined cake pan then pop it in the fridge while you make the filling.
Drain the cashews well. Add them to a high speed blender along with the Biscoff spread, cream cheese, maple syrup, coconut oil, apple cider vinegar, vanilla, and salt. Blend until completely smooth. If you don't have a high speed blender I recommend blending the cashews until pretty much smooth before adding the other ingredients to make it less work for the blender.
Remove the crust from the fridge and pour in the cheesecake filling. Tap a couple of times on the counter to knock out any air bubbles then put in the fridge to set for at least 6 hours, or overnight. Make sure it's level. Sit a small plate on the top of the pan to cover it.
Once the cheesecake is set, make the Biscoff topping by melting ½ cup of Biscoff gently until it's pourable but not too liquid. I pop mine in the microwave and heat in 10 second increments until it's ready. Or you can sit the jar in a bowl of hot water. Before pouring on the cheesecake check how warm it is. You don't want it to be hot or it will melt the cheesecake. Leave it to cool for a few minutes if necessary.
Carefully remove the cheesecake from the pan. Peel off the paper and remove from the base. Place on a plate, cake stand, or platter, then slowly pour the melted Biscoff spread over the top. If you want to be fancy you can swirl swooshy patterns into it with a spatula or pallet knife.
Decorate the top as desired with cookies and cookie crumbs then chill again to allow the cookie butter top to set.
NOTES
To make in an 8 or 9 inch springform or loose bottom pan increase all of the ingredients by 50% (multiply them by 1.5). Store the cheesecake in the fridge for up to 10 days. If making ahead for guests or a special occasion I recommend not decorating the top with cookies or crumbs until the day. The cookies absorb moisture from the cheesecake and can get a little soft when stored.