Wilt the spinach. Bring a large pan of salted water to a rolling boil, drop in the spinach, and blanch for 60 seconds. It will collapse from a mountain to a small dark-green tangle almost immediately, and the water will turn a deep emerald. Drain into a colander and press gently with the back of a spoon to squeeze out excess liquid — you want it damp, not dripping.

Soften the onion. Wipe the pan dry, set it over medium heat, and warm the olive oil until it shimmers. Add the diced onion and a pinch of salt, and cook for 5–6 minutes until the pieces turn translucent and smell sweet rather than sharp. Stir in the garlic and cook for 30 seconds more, just until the aroma hits you — garlic burns fast and turns bitter.

Build the filling. Tip the drained spinach back into the pan with the onion and garlic. Stir over low heat for 1 minute to drive off any remaining moisture, then scrape everything into a mixing bowl and let it cool for 5 minutes. Add the cream cheese, feta, cheddar, beaten egg, oregano, nutmeg, pepper and salt. Mix until you have a thick, scoopable paste with visible flecks of green and white.

Prepare the pastry. Heat the oven to 200°C (180°C fan, gas mark 6). Lightly flour your worktop, unroll the puff pastry, and cut each sheet into 6 equal rectangles, roughly 8 cm by 10 cm. You should have 12 rectangles in total. Work quickly — puff pastry hates warm hands, and once it softens it becomes sticky and hard to handle.

Fill and fold. Place a heaped teaspoon of filling in the centre of each rectangle, leaving a 1 cm border all the way around. Brush the border with egg wash, fold the pastry over the filling to make a small parcel, and press the edges firmly with the tines of a fork to seal. The fork marks should be deep and clear — shallow seals pop open in the oven.

Bake. Arrange the parcels on the lined tray, spacing them 3 cm apart so the hot air circulates. Brush the tops with egg wash and bake for 18–20 minutes, until the pastry has puffed into golden, layered domes and the kitchen smells buttery and toasted. If your oven runs hot on one side, rotate the tray at the 12-minute mark.

Rest before serving. Slide the tray onto a wire rack and leave the pastries alone for 5 minutes. The filling is molten straight from the oven and will scald anyone who dives in early — the rest also lets the pastry crisp up properly rather than steaming on the tray.