Whisk egg yolks and 50g sugar in a bowl until thick and pale.
Slowly boil milk and cream with remaining sugar and vanilla seeds.
Pour hot milk mixture into egg mixture while whisking continuously.
Cook mixture over gentle heat until thick enough to coat a spoon, then strain.
Heat 50ml water, 75g butter, and sugar, then cook peaches and basil until caramelised.
Heat deep-frying oil to 150°C in a heavy-based saucepan.
Boil 250ml water with sugar and butter, then beat in flour, baking powder, and egg.
Pipe batter into hot oil using a star-shaped nozzle and snip with oil-dipped scissors.
Fry churros in batches for 5-6 minutes until golden and dust with sugar.
Serve the churros alongside the peaches and custard.