To make the filling: In a large enameled saucepan or a small Dutch oven over medium heat, heat the oil. Sauté the onion until golden, 6 to 8 minutes. Add the chicken, parsley, cilantro, turmeric, saffron, water, ginger, and cinnamon. Cover and cook until the chicken is tender, 20 to 25 minutes. With a slotted spoon, transfer the chicken to a bowl and set aside to cool.

Let the sauce continue to simmer in the pan and add the beaten eggs, salt, pepper, and sugar. Stir constantly until the eggs are scrambled. Bone and shred the chicken and add it to the eggs. Set aside.

To make the almond mixture: In a blender or food processor, coarsely grind the almonds. Transfer them to a small bowl and mix them with the sugar and cinnamon. Set aside.

Preheat the oven to 425 degrees F. Remove 12 sheets of phyllo from the package and rewrap the remaining phyllo in its original plastic wrap. Refrigerate for another use.

Stack the 12 sheets on a work surface. Using a sharp knife, with a 12-inch pizza pan as a template, cut through the stacked phyllo sheets. Discard the scraps. With a pastry brush, paint the pizza pan with a little melted butter. Keep the phyllo leaves covered with a damp cloth as you work.

Layer 3 round phyllo leaves on the pan, lightly brushing each with melted butter. Sprinkle the third leaf lightly and evenly with the almond mixture. Layer and butter 3 more leaves. Spread the chicken mixture evenly over the top, leaving a 1-1/2-inch border of phyllo. Fold over the edges to partially cover the chicken mixture. Layer and butter 3 more leaves over the chicken, sprinkling the remaining ground almond mixture evenly over the top. Layer and butter the last 3 leaves of phyllo over the almond mixture. Tuck the edges of these last 6 leaves under the b'stila as you would a bed sheet.

Bake the b'stila until golden brown, 20 to 25 minutes. Place the powdered sugar in a fine-meshed sieve. Tap the sides of the sieve to cover the surface of the b'stila lightly and evenly with sugar. Using your thumb and forefinger, sprinkle ground cinnamon in 6 or 8 intersecting lines to create a diamond-shaped pattern, or use a paper doily or template to make your own individual design. Serve immediately, before the pastry becomes soggy.