Some Russian cooks substitute kasha for the rice in this dish.
- 1 tsp. active dry yeast
- 1 tsp. sugar
- 12 tbsp. plus 1 tsp. unsalted butter
- 2 cups flour, plus more as needed
- 3⁄4 cup sour cream
- 1⁄2 tsp. kosher salt, plus more to taste
- 3 eggs (1 whole, 2 hard-cooked and finely chopped)
- 2 tbsp. peanut oil
- 1 (8-oz.) boneless skinless salmon filet, cut into 1⁄2" pieces
- 1 (8-oz.) boneless skinless cod filet, cut into 1⁄2" pieces
- 1 yellow onion, finely chopped
- 10 oz. button mushrooms, finely chopped
- 1 cup cooked white rice
- 3 tbsp. finely chopped dill
- 2 tbsp. finely chopped flat-leaf parsley leaves
- 2 tbsp. vermouth
- 1 tbsp. fresh lemon juice
- 1 pinch freshly grated nutmeg
- Freshly ground black pepper, to taste
- 3 tbsp. dried bread crumbs
- 1 tsp. milk
- 1 egg yolk
In a small bowl, combine yeast, sugar, and 1⁄8 cup warm water; stir and let sit until foamy, about 10 minutes. In a large bowl, cut 8 tbsp. butter into chunks, combine with the flour, and, using your fingers, work butter into flour until it resembles coarse bread crumbs. Add yeast mixture, 1⁄2 cup sour cream, 1⁄2 tsp. salt, and the whole egg; stir to make a soft dough. Wrap dough in plastic wrap and chill for at least 2 hours or up to overnight.
Bring dough to room temperature. Grease a bowl with 1 tsp. butter. Turn dough out onto a floured work surface; knead, adding flour as needed, until smooth, about 5 minutes. Transfer dough to prepared bowl, cover with plastic wrap, and leave in a warm place until doubled in size, about 1 1⁄2 hours.
Heat oil and 2 tbsp. butter in a large skillet over medium-high heat. Add salmon and cod; cook, turning once, until just cooked, about 4 minutes. Transfer fish to a large bowl. Return skillet to medium-high heat; heat remaining butter. Add onions; cook until lightly browned, 3–4 minutes. Add mushrooms; cook for 5 minutes. Transfer to bowl of fish. Add remaining sour cream and the eggs, rice, dill, parsley, vermouth, lemon juice, nutmeg, and salt and pepper; stir to break up fish. Set filling aside.
Arrange oven rack in center of oven; heat to 400°. Halve dough; form 2 logs. On 2 lightly floured sheets of parchment paper, roll each dough log into a 10" x 16" rectangle. Transfer 1 dough sheet (on paper) to a foil-lined baking sheet; sprinkle with bread crumbs; spread filling over top, leaving a 1" border. Drape remaining dough over filling; remove paper; seal edges. Trim excess dough from edges, leaving a 1" border, and reserve scraps. Fold up edges of dough. Using corners of parchment paper, lift pastry log and invert onto baking sheet. Let rise for 15 minutes. Whisk egg yolk with milk; brush over top of dough. Roll out scraps, cut into decorative shapes, and press on top of dough; brush with egg mixture. Poke holes in top of dough; bake until golden, about 35 minutes. Let cool for 10 minutes before slicing to serve.