1. For the pastry: place the flour, sugar, salt and butter in a food processor. Blitz until the mixture resembles breadcrumbs, and the biggest pieces of butter are no bigger than a pea. Add the egg and blitz again until the dough comes together. You can also do this by hand, rubbing the butter into the dry ingredients and bringing together with the egg. Refrigerate for at least two hours.
2. Roll out the pastry to about 3-5mm thick, and cut out circles slightly bigger than your tartlet tins (mine were 10cm diameter, so I cut out 14cm circles). Line the tartlet tins, pressing the pastry firmly into the corners so that it doesn’t shrink in the oven. Refrigerate while you preheat your oven to 170 degrees/150 fan (or up to 24 hours). Line each tartlet with a disc of baking parchment and fill with baking beans, ensuring they cover the entire base of the tin.
3. Bake for about 15 minutes, until the sides are beginning to turn golden. Remove the baking beans and paper, and egg-wash the tartlet bases, before returning to the oven for 5-8 minutes, until even and golden brown. Allow to cool fully.
4. For the crème patissière: place the milk and the vanilla bean extract in a saucepan over a medium heat until just below simmering point. Meanwhile, place the yolks, sugar, cornflour and salt in a bowl and whisk until fully combined. Slowly pour in the hot milk mixture, whisking all the time. Return this mixture to the saucepan, and whisk over a low heat until it thickens and just starts to bubble. Pour into an airtight container and chill.
5. To assemble: dehull and slice the strawberries into quarters or eighths. Slice the basil finely, leaving a few leaves to garnish. Place the strawberries, basil and icing sugar in a bowl, stir gently and leave to macerate for 10 minutes.
6. Whip the cream to stiff peaks, but do not overbeat (you don’t want to make butter). Fold the whipped cream into the crème pat, and place in a piping bag with a 5mm nozzle. Pipe into each of the tartlet cases (you can also do this with a spoon, and level with a palette knife). Arrange the strawberries on top, and garnish with a basil leaf.