01 - Preheat oven to 375°F. Line a baking tray with parchment paper.
02 - Heat a large skillet over medium heat with a splash of olive oil. Sauté onion until soft and translucent, about 3 minutes. Add garlic and cook for an additional minute.
03 - Add spinach to the skillet and cook, stirring, until wilted and all liquid evaporates. Remove from heat and let cool for 5 minutes.
04 - In a large bowl, combine the cooled spinach mixture with crumbled feta, chopped dill, egg, black pepper, nutmeg (if using), and salt to taste. Mix until evenly incorporated.
05 - Lay one phyllo sheet on a clean surface and brush lightly with melted butter. Place a second sheet on top and brush again. Cut the double-layered sheets lengthwise into 3 long strips.
06 - Place one tablespoon of filling at one end of each strip. Fold the corner over to form a triangle, continuing to fold the strip while maintaining the triangle shape until completely folded. Brush the exterior with melted butter.
07 - Repeat the layering, cutting, filling, and folding process with the remaining phyllo sheets and filling.
08 - Arrange all triangles on the prepared baking tray. Bake for 20–25 minutes until golden and crisp.
09 - Allow to cool slightly before serving.