Combine the flour, almond meal, cacao, Natvia and butter in a food processor and pulse until it resembles breadcrumbs.
Add the cream and pulse until it just looks like it will come together. Pour onto the bench top and bring together quickly with your hands.
Form into a disk and then wrap tightly in plastic before refrigerating for 1 hour.
Make the mousse by melting the dark chocolate in the microwave. Stand to cool. Whisk eggs for 5 minutes until thick and creamy. Add the Natvia, vanilla and the melted cooled chocolate and fold in gently.
Whisk the cream until thick and creamy and then fold the chocolate mixture through until combined and smooth. Cover and refrigerate. Preheat the oven to 170C.
Roll out the pastry and cut into rounds that fit into a ⅓ cup capacity cupcake tray. Place the pastry in the greased tart in, and ensure the edges come up the sides of the mould. Prick holes in the bottom. Place in the freezer for 30 minutes.
Bake for 25 minutes. Remove from the oven and allow to cool completely. Carefully remove the shells form the cupcake tin. Fill with the filling and refrigerate for at least 1 hour.