Preheat the oven to 200°C (180°C fan) and line a large baking tray with baking paper. While it heats, place the sliced strawberries in a medium bowl. Sprinkle over the caster sugar, cornflour, vanilla extract, and lemon juice. Toss gently with your hands until every piece of strawberry is coated. You’ll see the sugar begin to draw out the juices, turning the mixture glossy and fragrant.

Make the cream cheese layer. In a separate small bowl, beat the softened cream cheese with the icing sugar, lemon zest, and a pinch of sea salt until it’s smooth and pillowy, with no lumps. The texture should be spreadable but not runny—think thick yoghurt.

Prepare the pastry. Unroll the puff pastry sheet onto a lightly floured surface. Use a sharp knife to cut it into 8 equal rectangles. With the tip of the knife, score a border about 1cm from the edge of each rectangle, being careful not to cut all the way through. This border will puff up beautifully, creating a rim for the filling.

Assemble the pastries. Spread a generous teaspoon of the cream cheese mixture inside the scored border of each pastry rectangle, keeping it away from the edges. Spoon the strawberry mixture on top of the cream cheese, dividing it evenly. You should have a neat mound of berries sitting within the border. The smell of lemon and vanilla will already be filling your kitchen.

Brush and sprinkle. Using a pastry brush, lightly coat the exposed pastry borders with the beaten egg. You’ll see the pastry turn a glossy yellow. Sprinkle the demerara sugar over the borders—this gives a delightful crunch and a caramelised sheen when baked.

Bake until golden. Place the tray in the preheated oven and bake for 18-20 minutes. At the 15-minute mark, check the pastries: the borders should be puffed and golden brown, and the strawberry filling should be bubbling gently at the edges. The kitchen will smell like a bakery—sweet, buttery, and fruity all at once. If the borders are browning too quickly, loosely cover the tray with foil for the final 3 minutes.

Cool and serve. Remove the tray from the oven and let the pastries rest on the tray for 5 minutes. This is crucial—the filling will be lava-hot straight out of the oven, and resting allows it to set slightly so you don’t burn your tongue. Transfer to a wire rack if you want them to cool faster, or serve warm directly from the tray for maximum comfort.