Line a 9 inch round tart pan with a round piece of parchment paper on the bottom and set aside.
To a food processor, add the almonds, cocoa powder, salt and syrup and process until clumps form. (see video) This will yield a nutty coarse texture for the crust. If you prefer a more finely ground one, process the dry ingredients into a flour first and then add the syrup.
Get a small bowl of water and dip your fingertips in it and press this mixture into the tart pan making sure it is flat and even along the bottom and press against the edges. It is very sticky and the water helps immensely. Place a piece of parchment paper on top and really press it down hard so it is compact.
Wipe down the food processor making sure to remove any remaining bits of nuts.
For the filling, cook your potato either in the microwave or bake it. I don't advise boiling it, as that will add too much moisture to the potato and affect the result of the tart. Let it cool a few minutes and then mash the potato and measure out exactly one packed cup (240g). Add the potato to a food processor.
Add the chocolate chips to a bowl and pour the milk over them. Either melt in the microwave or a double boiler. I use the microwave for 2 30 second intervals, stirring in between each 30 seconds. Remove the chocolate stir until completely melted. Add this to the food processor.
Add the vanilla, espresso and salt to the food processor. Process for 1-2 minutes until 100% smooth and creamy. Try your best not to eat it at this stage. It will be hard, but I have faith in you.
Pour this amazing bowl of chocolate heaven over the crust and smooth out with the back of a spoon to create a flat top. Jiggle the tart pan gently to help flatten it out.
Place the tart in the fridge to completely set and firm up. 2-4 hours at least. You can even leave it overnight and it will be perfect and sliceable immediately upon removal from the fridge.
To release the tart, carefully push up from the bottom, going around the circle gently pressing underneath to pop it out. This will help the chocolate to release. I let mine set overnight, so I removed it about 15 minutes or so and let it sit before removing the tart. Mine was a breeze to remove.
Slice and serve with raspberries, chocolate or a dusting of cocoa powder!