Nazook (Sweet Persian Pastry)

In a bowl, combine the sour cream, 2 teaspoons of sugar, and yeast. Let stand for 5 minutes to allow the yeast to activate. (5 minutes)

Stir in the egg, vinegar, and oil until well combined. (2 minutes)

In a separate large bowl, add 3 cups of flour. Cut in the cold, cubed butter using a pastry blender or two knives until the mixture resembles coarse crumbs. (10 minutes)

Stir in the sour cream mixture until a dough forms. (5 minutes)

Turn the dough out onto a lightly floured surface and knead until smooth but slightly tacky, about 10 minutes. (10 minutes)

Divide the dough into 4 equal pieces and wrap each piece tightly in plastic wrap. Refrigerate for at least 2 hours, or preferably overnight, to allow the dough to firm up. (2 hours)

Preheat the oven to 350 degrees F (175 degrees C).

In a very large bowl, combine the 2 1/2 cups of sugar, melted butter, and vanilla extract. Stir in the remaining 4 cups of flour until well combined. Gently fold in the egg whites. (10 minutes)

On a lightly floured work surface, roll out one piece of dough into an 8x12-inch rectangle. (5 minutes)

Crumble one-quarter of the filling mixture evenly over the dough, leaving a 1/2-inch border on the long sides. (5 minutes)

Cover the filling with plastic wrap and gently flatten it into the dough using a rolling pin. (2 minutes)

Starting from one of the long sides, roll the dough tightly into a log. (3 minutes)

Using a sharp knife, cut the log into 2-inch pieces at a slight angle. Arrange the pieces on a rimmed baking sheet, leaving some space between each piece. Gently push down on the top of each piece to flatten it slightly. (15 minutes)

Repeat steps 9-13 with the remaining dough and filling. (45 minutes)

In a small bowl, whisk together the egg yolks and yogurt. Brush the mixture evenly over the tops of the dough pieces to create a golden glaze. (5 minutes)

Bake in the preheated oven for 20-30 minutes, or until the Nazook are golden brown and cooked through. (30 minutes)

Remove from the oven and let cool on the baking sheet for about 15 minutes before serving. (15 minutes)