Preheat the oven to 170°C (340°F). Grease a 9-inch springform pan and set aside.
Make the crust: In a bowl combine the All-Purpose Flour with a pinch of Salt and Sugar. Cut cold Unsalted Butter into the dry ingredients until the mixture resembles coarse crumbs, then stir in one Egg and knead briefly to form a smooth dough. Wrap the dough and chill in the refrigerator for 30 minutes.
Roll the chilled dough out on a lightly floured surface and press it into the bottom (and slightly up the sides) of the prepared pan. Prick the base with a fork and blind-bake for 10–12 minutes until just set and lightly golden. Remove from the oven and lower the oven temperature to 160°C (320°F).
Prepare the filling: In a large bowl break up and beat the Full-Fat Twaróg until smooth. Add the remaining Egg, additional Sugar to taste, and melted Unsalted Butter, mixing until fully incorporated.
Add the Potato Starch, Vanilla Extract, and Lemon Zest to the cheese mixture, plus a small pinch of Salt. Fold in the Raisins (you can soak them briefly in warm water or rum if you like), mixing until even.
Pour the filling into the pre-baked crust and smooth the top. Bake at 160°C (320°F) for 60–75 minutes, or until the center is mostly set but still slightly jiggly — it will firm as it cools.
Turn off the oven and let the cheesecake cool inside with the door ajar for about an hour to minimize cracking, then transfer to a wire rack. Chill thoroughly in the refrigerator for at least 4 hours or overnight.
Before serving, dust the top with Powdered Sugar. Slice and enjoy chilled or at cool room temperature.
