Instructions:
- Heat olive oil in a large non-stick frying pan. Sauté the minced shallot until translucent, about 3 minutes.
- Add the spinach in batches and cook until fully wilted. Remove the mixture from the heat and allow it to cool completely. Crucially, squeeze out ALL excess moisture from the spinach mixture using a clean tea towel.
- Transfer the cooled, dry spinach mixture to a mixing bowl. Stir in the nutmeg, salt, pepper, chopped dill, and the egg yolk.
- Gently fold in the crumbled Feta cheese, taking care not to overmix.
- Preheat oven to 400°F (200°C). Line two baking sheets with parchment paper.
- Unroll the puff pastry sheet. Cut the pastry into two equal halves lengthwise, then cut each half into 8 equal squares or rectangles, yielding 16 pieces total.
- Place about 1 tablespoon of filling onto one half of each pastry piece, leaving a clean 1/2-inch border. Brush the edges with the beaten egg wash.
- Fold the other half of the pastry over the filling to create a triangle or rectangle pocket. Crimp the edges firmly with a fork to seal completely.
- Place the sealed crisps onto the prepared baking sheets. Brush the tops generously with the remaining egg wash and sprinkle with sesame seeds, if using.
- Bake for 18–20 minutes, or until the pastry is deeply puffed and golden brown.
- Transfer to a wire rack to cool slightly before serving warm.