Preheat the oven to 200°C/Fan 180°C/400°F. Take a 20–22cm (8–9 inch) tatin tin or shallow flameproof casserole dish and trim your puff pastry sheet to be the same diameter. Set aside.

Snap the ends from the asparagus stems, then trim the stems so they fit exactly into your prepared tin. Set aside. Place the tatin tin or flameproof casserole dish over a medium-high heat and add the butter and bacon. Fry for 2–3 minutes until golden. Add the asparagus to the pan and cook for 1 minute, turning occasionally and shaking the pan so they cook evenly.

Remove the pan from the heat and carefully place the pastry sheet over the asparagus in the pan and press down, tucking the pastry edges under as you go. Pierce the top with a knife to allow the steam to escape and transfer to the oven. Cook for 25 minutes or until the pastry is risen and golden. If the top is becoming too brown, pop a little foil loosely over the top.

Remove from the oven and leave to cool for 5 minutes. Finally, upturn onto a plate or board and serve hot.