Place a saucepan over medium heat.
From a chilled can of coconut milk, scoop the cream only and place into the pan. Allow cream to melt. (You will not be using the water in the coconut milk for this recipe so you may discard it or reserve it for something else.)
Add in 3 blocks from the chocolate baking bar and the instant coffee. Whisk ingredients together until the chocolate has melted and you have a rich, creamy sauce.
Pour the chocolate mixture into the cooled tart crusts. Make sure to fill up to the crust brim only, as it will pour over if you pour too much or too quickly.
Carefully place the tarts in the fridge and leave overnight.
When the filling is set, gently pop the tarts out of the ring mold by pressing with all fingertips at the bottom and working your way around the ring.