Method

• 1.
  For custard, whisk yolks, cornflour and sugar in a bowl until smooth. Place cream and chocolate in a saucepan over medium-low heat and stir until chocolate melts. As soon as cream mixture starts to bubble, pour it onto egg mixture, whisking continuously but gently until combined. Strain through a fine sieve into a clean bowl and cover the surface directly with plastic wrap to prevent a skin forming. Refrigerate overnight.
• 2.
  Beat butter and sugar in a stand mixer fitted with the paddle attachment until pale. Fold in flour, baking powder, nutmeg and egg until a soft dough forms. Pat into a flat disc, wrap in plastic wrap and chill overnight.
• 3.
  The next day, preheat oven to 180°C. Roll out pastry between 2 lightly floured sheets of baking paper to 3mm thick. Use pastry to line base and sides of a 22cm loose- bottomed, fluted tart pan, trimming any excess, then place in freezer for 10 minutes. Line pastry with baking paper and pastry weights, place on a baking tray and bake for 20 minutes or until edges are pale golden. Remove weights and paper and bake for a further 10 minutes or until base is golden. Remove from oven and cool.
• 4.
  Reduce oven to 140°C. Strain chilled custard through a sieve, then pour into cooled pastry case. Bake for 1 hour 20 minutes or until edges are set with a gentle wobble in the centre. The sugars caramelise a tiny bit on top, but the texture inside is silky smooth. Cool to room temperature, then chill for 4 hours or until set. Dust with extra nutmeg to serve.