To begin, whisk flour, sugar, and salt in a large bowl. Add the cold butter cubes and rub gently with fingertips until the mixture resembles coarse crumbs. Transition to adding water.

Sprinkle in cold water a tablespoon at a time, mixing lightly until the dough just comes together. Avoid overworking to maintain flakiness. Shape into two discs, wrap in cling film, and chill for 30 minutes.

Preheat your oven to 200°C (400°F). Place a baking tray inside to heat, which helps the base crisp evenly. Prepare the filling while the dough rests.

In a bowl, combine partridgeberries, sugar, flour, lemon juice, and zest. Stir gently to coat the berries evenly. Add butter just before filling the crust.

On a lightly floured surface, roll one dough disc into a circle about 30 cm wide. Line a 22 cm pie dish with the dough, leaving an overhang. Transition to adding the filling.

Pour the berry mixture into the prepared crust. Dot with small pieces of butter for richness. Transition to rolling and shaping the lattice.

Roll out the second dough disc into a rectangle about 3 mm thick. Cut into even strips (around 1.5–2 cm wide). Lay half the strips across the pie, evenly spaced. Weave the remaining strips over and under to form a lattice. Trim excess pastry and crimp the edges to seal.

Place the pie on the preheated tray and bake for 20 minutes at 200°C. Reduce heat to 180°C (350°F) and bake for another 25–30 minutes until golden brown and the filling bubbles through the lattice. Proceed to cooling.

Remove from the oven and allow to cool on a rack for at least 30 minutes. This resting time helps the filling set. Prepare for serving.

Slice the pie and serve slightly warm with cream or custard. Presentation tip: Brush the lattice with a little egg wash before baking for a glossy finish.