Instructions

1. Twenty four hours before you plan to make the triangles, thaw 8 ounces or 1 pound phyllo dough (depending on the brand) in the refrigerator, wrapped in the plastic it came in. Cook the rice or grain if needed and refrigerate.
2. The next day, take the phyllo out of the refrigerator and let it sit at room temperature in its wrapping while you make the filling.
3. Arrange a rack in the middle of the oven and heat the oven to 350°F. Line a baking sheet with parchment paper.
4. Strip the leaves from 2 bunches sturdy greens (reserve the stems) and coarsely chop until you have 7 packed cups. Finely chop the stems until you have 2 cups. Finely chop 1 small yellow onion (about 1 cup).
5. Heat 2 tablespoons olive oil in a large sauté pan over medium heat until shimmering. Add the stems and onions and cook, stirring occasionally, until tender but not browned, 5 to 6 minutes. Add the leaves and cook, stirring frequently with a wooden spoon, until wilted and tender, 5 minutes. Meanwhile, finely chop 2 garlic cloves.
6. When the greens are tender, add the garlic and 5 ounces baby spinach or other tender greens (about 5 cups) to the pan a few handfuls at a time, stirring constantly, until the spinach is wilted, 2 to 3 minutes.
7. Transfer the mixture to a colander set in the sink. Using a wooden spoon or rubber spatula, press the greens mixture against the sides of the colander to extract as much liquid as possible, stirring occasionally to make sure you get most of the moisture out. Transfer the mixture to a large bowl.
8. Finely chop fresh dill until you have 1/4 cup (or use 2 tablespoons dried dill) and crumble 6 ounces feta cheese (about 1 cup). Add the dill, feta, 1 cup cold cooked rice or other grain, 1/2 teaspoon grated nutmeg, 1/2 teaspoon kosher salt, and 1/4 teaspoon black pepper to the greens and mix until combined. Taste and season with more kosher salt and black pepper as needed. Add 2 large eggs and stir until combined.
9. Melt 1 stick unsalted butter in the microwave or on the stovetop. Carefully unroll the phyllo dough. Pick up 1 sheet of dough and lay it out on a large cutting board with a long side closer to you. Cover the remaining stack of dough with a clean dish towel to keep it from drying out. Drizzle the phyllo sparingly with melted butter and brush it evenly over the phyllo.
10. Place a second sheet of phyllo directly on top of the buttered sheet and press gently to glue the sheets together. Using a sharp knife, cut the dough vertically into 4 strips, each about 3 1/2 inches wide.
11. Place about 2 tablespoons of the greens mixture on the bottom left corner of one of the phyllo strips. Bring the lower left-hand corner of the strip up and to the right diagonally so the bottom edge of the strip lines up with the right side of the strip, creating a triangle. Fold the pocket upwards and then to the left and so on, as you would fold a flag.
12. Before making the last fold, brush the dough with butter, then fold over the triangle. Brush the triangle lightly with butter and place on the baking sheet. Working quickly so the dough doesn’t dry out, fill and fold the remaining 3 layered phyllo strips to make 4 triangles.
13. Repeat with the remaining dough and filling to make 24 to 32 pockets. If you run out of butter (you’ll end up with a few tablespoons of milky liquid at the bottom of the cup), add just enough melted butter or olive oil to finish the job.
14. Bake the pockets until golden brown, 20 to 25 minutes. Let cool 5 to 10 minutes before serving. (Alternatively, freeze the unbaked pockets on the baking sheet until solid and then transfer them to a zip-top bag. The triangles can be stored in the freezer for up to 3 months. Bake the frozen triangles for 25 to 30 minutes.)