For the pastry, put the egg yolk, butter, sugar and ½ tsp salt in a processor and pulse until creamy and soft. Add the flour and pulse until the mix comes together in clumps, but don’t overwork it. Tip onto the work surface and squish the dough together to make a smooth disc. Wrap and chill for 30 mins.
For the filling, beat the butter, sugar, egg, extract and almonds together until creamy, then fold in the flour and a pinch of salt.
Line a large, flat baking sheet with parchment. Roll the pastry on a floured surface until just thicker than a £1 coin. Stamp 16 x 9cm circles using a pastry cutter, re-rolling the trimmings. Put 8 of the rounds on the sheet, allowing a little space between each one. Spoon 1 tbsp of the filling onto the middle of the rounds, flatten it out a little, then press in 6 gooseberries, pointy end up, in a flower shape.
Briefly beat the egg white with a fork until frothy. Brush some of this over the remaining circles, then sit them on top of the berries, like hats – the pastry on top will fold itself over the berries as it cooks. Sprinkle with the 25g sugar and chill while you heat oven to 190C/170C fan/gas 5. Bake the pies for 35 mins or until golden. Serve warm with cream or ice cream.