Method

• 1.
  Place biscuits in a food processor and crush to fine crumbs. Add melted butter and pulse to combine. Press into base and sides of a 23cm x 3cm loose-bottomed tart pan. Chill for 30 minutes until firm.
• 2.
  Place the ricotta in a food processor and process until smooth. Place in a bowl, then fold in the mascarpone, icing sugar, vanilla and liqueur. Finely chop half the chocolate and fold through the mixture. Spread the filling into the tart shell and chill for at least 1 hour.
• 3.
  Meanwhile, melt the remaining 150g chocolate in a bowl set over a pan of gently simmering water (don’t let the bowl touch the water). Stir until melted and smooth, then spread over a flat tray and set aside at room temperature to harden. Using a sharp knife or vegetable peeler, draw long strokes across the top of the chocolate to make rough shards. Remove the tart from the pan, place on a serving plate, then decorate with chocolate shards.