Preheat the oven to 200C/180C Fan/Gas 6. Sift the flour and a pinch of salt into a bowl. Stir in the icing sugar and rub in the butter with your fingertips until it looks like breadcrumbs. Sprinkle over 2tbsp chilled water and mix with a knife until it forms clumps. Gather with your hands to make a dough.
Put the pastry on a floured surface and roll out to the thickness of a £1 coin. Use to line a 23cm flan case. Prick the base and lay some baking powder inside. Weigh the paper down with dry rice. Bake for 10 minutes. Remove the paper and rice and return to the oven for another 5 minutes. Reduce the oven to 160C/140C Fan/Gas 3.
Break the chocolate into squares and put in a bowl. Heat the cream until it is almost boiling and then pour over the chocolate. Stir until the chocolate melts.
In another bowl, whisk the caster sugar, eggs, and vanilla until creamy. Pour on the chocolate, stirring, then pour into the pastry case and cook in the oven for 25 minutes. Leave to cool.
Slice the strawberries. Serve some on the flan and the rest separately.