Follow these step-by-step instructions to prepare your Spinach and Feta Spanakopita Triangles:

Preparing the Filling

1. Sauté the Onions and Garlic: Heat olive oil in a large skillet over medium heat. Add the chopped onion and sauté until it becomes translucent. Add the minced garlic and sauté for another minute until fragrant.
2. Cook the Spinach: Add the chopped spinach to the skillet, stirring occasionally until the spinach is wilted and the moisture has evaporated. This should take about 5 to 7 minutes. Remove from heat and let it cool.
3. Mix the Filling: In a large mixing bowl, combine the cooked spinach mixture, crumbled feta cheese, beaten eggs, chopped dill, parsley, nutmeg, salt, and black pepper. Stir until all ingredients are well combined.

Assembling the Triangles

4. Prepare the Phyllo: Unroll the thawed phyllo dough and keep it covered with a damp kitchen towel to prevent it from drying out.
5. Layer the Phyllo: Take one sheet of phyllo dough and brush it lightly with melted butter. Place another sheet on top and brush it with butter again. Repeat this process until you have three layers.
6. Cut the Phyllo: Using a sharp knife, cut the phyllo layers into strips approximately 3 inches wide.
7. Fill and Fold the Triangles: Place a tablespoon of the spinach filling at the end of each phyllo strip. Fold the corner of the strip over the filling to form a triangle. Continue folding, maintaining the triangle shape, until you reach the end of the strip. Brush the end with melted butter to seal it.
8. Repeat: Continue this process with the remaining phyllo sheets and filling.

Baking

9. Preheat the Oven: Preheat your oven to 350°F (175°C).
10. Arrange and Bake: Place the triangles on a baking sheet lined with parchment paper. Brush the tops with more melted butter for a golden finish. Bake in the preheated oven for 20 to 25 minutes, or until the triangles are golden brown and crisp.
11. Cool and Serve: Allow the Spanakopita triangles to cool slightly before serving. Enjoy them warm or at room temperature.