Method

• 1.
  Cream the butter, icing sugar and cocoa powder in the bowl of a stand mixer fitted with the paddle attachment on medium speed. Add the egg yolks, mixing well and scraping down the side of the bowl as necessary.
• 2.
  Add the dry ingredients. Mix only until the pastry comes together, then stop. Press the dough into an even, flat square, enclose in plastic wrap and place in the refrigerator to rest for 1 hour or until firm.
• 3.
  Preheat the oven to 170°C.
• 4.
  Roll out the dough on a lightly dusted work surface to a thickness of 3mm and line the base and side of a 22cm tart ring. Place the tart shell in the refrigerator for 10 minutes to firm up.
• 5.
  Using a small sharp knife, trim the top edge of the pastry so it’s flush with the top of the ring. Cut out a 25cm circle of baking paper and crumple it into a ball. Open out the paper and use it to line the unbaked shell, then fill shell with baking weights or uncooked rice. Bake for 17 minutes or until slightly darkened. Remove the tart from the oven and leave to cool at room temperature for 5 minutes. Remove weights and paper.
• 6.
  Increase oven to 180°C.
• 7.
  Melt the chocolate, cocoa powder and butter in a double boiler or in a heatproof plastic bowl in the microwave. Cool slightly. In a separate bowl, lightly whisk the eggs and sugar by hand. Fold in the dark chocolate mixture, followed by the sifted flour. Continue gently folding using a spatula until well combined.

• 8.
  Place the finished mixture into the par-baked tart shell and bake for 14-15 minutes until just set with a slight wobble in the centre.
• 9.
  Let the tart cool at room temperature for 5 minutes before removing the tart ring.