Mix the flour, sugar and salt in a bowl. Add the butter and rub together using your hands to form an even, crumbly mixture. Add the egg, mix quickly to create a soft dough – do not knead. Roll out the pastry on a lightly floured surface, place in the prepared tin, prick firmly, chill for approx. 30 mins.
To blind bake
Approx. 20 mins. in the lower half of an oven preheated to 220°C. Remove from the oven, allow to cool slightly, remove from the tin, place on a cooling rack and allow to cool completely.
White chocolate mousse
Melt the chocolate and 2 tbsp of cream in a thin-sided bowl over a gently boiling bain-marie, stirring until smooth. Remove the bowl, leave the chocolate to cool. Beat the remaining cream until stiff. Carefully fold the whipped cream and reserved chocolate into the chocolate mixture using a rubber spatula. Spread the mousse over the cake base, cover and chill for approx. 1 hr.
Scatter the pomegranate seeds over the tart, cover again and chill for approx. 1 hr.