1. 1. In a large mixing bowl, combine cold water and flour. Mix until a dough forms.

2. 2. Add cold butter to the dough and continue mixing until the butter is fully incorporated.

3. 3. On a lightly floured surface, roll out the dough to about 3 mm thickness.

4. 4. Using a cookie cutter or the rim of a glass, cut out circles from the rolled-out dough.

5. 5. Place a spoonful of prawns in the center of each dough circle.

6. 6. Sprinkle the prawns with salt, pepper, and chopped dill.

7. 7. Fold the dough over to form a triangle, pressing the edges to seal. Crimp the edges with a fork to ensure they are secure.

8. 8. Brush the tops of the pastries with heavy cream.

9. 9. Bake the pastries in a preheated oven at 190°C (375°F) for 15 to 20 minutes, or until golden brown.

10. 10. Serve the pastries warm, garnished with cucumber slices. Be cautious when serving hot pastries to avoid burns.