Melt a knob of butter in a pan and add the mustard seeds followed by the baby spinach. Cook till wilted then keep aside.
Add oil to the same pan and sauté the curry leaves and onion, then add the garlic and a knob of butter. When softened add the curry powder and lightly cook till fragrant then add the cooked rice. Make sure it's all well coated then add the chopped coriander, lemon zest, chopped hard boiled eggs and season. Leave to cool slightly.
Lay out your puff pastry, on the sheet it came on, on a baking tray. Squeeze the liquid out of the wilted spinach and lay down the centre of your pastry. Season the salmon on both sides and lay on top of spinach. I used my hands to then scoop and press the rice mixture on the top. Carefully fold the pastry over from each side, securing with a bit of egg wash, then fold over the ends, again securing with the egg wash. Carefully roll it over so the seam is on the bottom and remove the pastry paper. I made a lattice with another piece of pastry from the top, but you can leave plain or even create your own decoration. Cover all over with egg wash. Pierce three tiny ones with a cocktail stick or small skewer along the top to allow excess steam to escape.
Bake in a preheated oven at 200c for 30 minutes.
