Mix the flour, salt, bicarbonate of soda, cocoa powder and icing sugar in a bowl. Add the margarine and rub together by hand to form an even, crumbly mixture. Press together quickly to form a dough, do not knead, cover and refrigerate for approx. 30 mins. Press the dough into the prepared baking tray by hand, creating a rim around the edge approx. 2 cm high. Place some baking paper on the dough base and cover it thickly with dried pulses (e.g. kidney beans).
To blind bake
Approx. 15 mins. in the lower half of an oven preheated to 180°C. Remove from the oven, remove the baking paper and pulses, allow to cool slightly, remove the tart base from the tray and leave to cool on a rack.
Heat the chocolate and coconut milk in a small saucepan on a low heat, stirring constantly until it melts. Pour onto the tart base.
Sprinkle the pomegranate seeds over the chocolate. Cover the tart and leave to chill for approx. 3 hours.