Preheat oven to 190°C fan / 375°F / Gas 5. Peel, halve, and core the apples. Drop into lemon water to prevent browning.
In an ovenproof 24 cm frying pan, melt the butter and sugar over medium heat. Add the lemon juice, vanilla, cinnamon stick, star anise, and a pinch of salt. Cook gently, swirling occasionally, until the sugar dissolves and the caramel turns deep amber.
Drain and pat the apples dry. Arrange them rounded side down in the caramel. Cover with a parchment cartouche (with a small steam hole). Simmer for 10-12 minutes, basting occasionally. The cartouche keeps the apples moist and evenly cooked.
Remove the cartouche. Drape the pastry over the apples and tuck in the edges. Prick a few holes for steam to escape. Bake for 25-30 minutes, until golden and puffed.
Let rest for 5-10 minutes. Remove cinnamon and star anise. Place a plate over the pan and flip carefully - hot caramel may spill, so use caution.
Cut into wedges and serve with a generous spoonful of clotted cream and a fresh mint sprig. Drizzle over any leftover pan caramel if desired. Smacznego!