Preheat the oven to 200°C (180°C Fan, Gas Mark 6). On a lightly floured surface, roll out the pastry to fit a 2cm (3/4inch) deep, 23cm (9 inch) diameter loose-bottomed, fluted flan tin. Trim the pastry, line a piece of baking parchment and fill the centre with baking beans or raw rice.
Put the tin on a baking tray and bake for 10 minutes. Carefully remove the paper and the beans or rice, prick the base and return to the oven for 7-8 minutes to lightly brown the pastry. Leave to cool then carefully remove from the tin and place on a serving plate.
Using a vegetable peeler, shave off small pieces (approx. 25g) of the White Chocolate and put aside for decoration.
Break the remaining White Chocolate into a large heatproof bowl. Put the bowl over a saucepan of barely simmering water and leave to melt. Remove the bowl from the pan of water and leave aside for 10 minutes to cool.
Stir in the coconut milk and Sicilian lemon extract and mix well. Pour into the pastry case and chill for at least 2 hours to set.
To decorate, sprinkle the top with toasted coconut and the White Chocolate shavings you reserved earlier. Serve immediately.