Line a 23 cm (9 inch) fluted flan tin with the pastry. Trim the edges, then press the pastry firmly into the grooves so the rim sits a little higher than the tin. Fill with scrunched-up nonstick baking paper and baking beans, then bake in a preheated oven, 180°C (350°F), Gas Mark 4, for 15 minutes. Remove the paper and beans and bake for a further 5 minutes. Set aside to cool.
Mix the egg yolks, cornflour and sugar in a bowl. Put the milk in a heavy-based nonstick pan and bring to the boil. Pour over the egg mixture and blend well using a balloon whisk. Add the vanilla essence, then return to the rinsed-out pan and bring to the boil, whisking continuously until boiled and thickened. Transfer to a bowl to cool, stirring occasionally. Cover with clingfilm to prevent a skin forming.
Place the cooled pastry case on a serving plate and fill with the custard using a metal spoon to swirl up to the rim. Put the fruit in a bowl and toss to mix, then loosely arrange over the top of the custard. Dust with icing sugar and serve in wedges with spoonfuls of crème fraîche or yogurt.