Add oreos to the bowl of a food processor and blitz for a couple of minutes until the mixture resembles a sand-like texture. Add in melted dairy-free spread and continue to mix for 30 seconds to a minute until the mixture is wet and sticky. Tip the mixture into a 25 cm non-stick tart pan with a removable base. Use your fingers or the base of a glass to press the mixture down and to the edges and up the sides ensuring it is all compressed down and evenly distributed. Set aside in the fridge while you make the filling.
Chop up chocolate into small pieces and place in a large, glass bowl. Set aside.
In a small saucepan, heat coconut milk, maple syrup and vanilla, stirring until just starting to simmer. You want it to be nearly boiling but not quite.
Pour the hot coconut milk mixture over the bowl of chocolate and let sit for 5 minutes. Stir chocolate mixture until smooth, shiny and creamy.
Pour the chocolate ganache filling into the prepared tart base and set aside in the fridge to chill for 4 hours until set.
To serve, top tart with fresh berries and a dusting of icing sugar. Keep chocolate tart refrigerated.