Recipe Courtesy Chef Dimitriy Sikalskiy, Sabres Restaurant, Toronto.
In a large bowl, combine the flour and salt. Add the butter and shortening, using your finger tips rub the flour and fat together until resembles coarse meal. Pour water over the mixture all at once, toss together lightly and gather into a ball. If the dough seems crumbly add 2 tbsp more of cold water. Divide the dough in half. Dust each half with flour and wrap them separately in plastic wrap. Refrigerate for 1 hour.
Combine water, wine, coarsely chopped onions, celery, carrots, peppercorns and salt in a large Dutch oven or casserole. Bring to a boil over high heat. Lower the salmon into the liquid and reduce the heat to low. Simmer until fish is firm to the touch, about 8 to 10 minutes. With a slotted spatula, transfer the fish to a large bowl. Cool fish until easy to fork with. Using your fingers or a fork, separate fish into small flakes.
Melt butter in the skillet over high heat. Add onions and mushrooms. Reduce the heat to medium and cook until onions are soft but not browned, about 3 to 5 minutes. Season the onions and mushrooms with salt and pepper. With a slotted spoon, transfer the onions and mushrooms to a large bowl. Add cooked rice and lemon juice. Toss to combine.
Add the hard-cooked eggs and dill to the flaked salmon and toss together lightly but thoroughly. Add the rice mixture. Toss lightly but thoroughly to combine. Taste for seasoning.
Preheat the oven to 400 degrees F.
Beat the egg yolk and cream with a fork to make an egg wash. Set aside.
Place one half of pastry dough on a floured surface. Roll into a rough rectangle about 1-inch thick. Dust with flour and roll until the dough is about 1/8 inch thick, and then trims it to a rectangle, about 7×16-inches.
Grease a baking sheet with butter.
Drape the pastry over a rolling pin and unroll it over the buttered baking sheet. Place the filling along the length of the pastry, leaving a 1-inch border so dough is exposed around the filling. With a pastry brush, brush the exposed border of dough with the egg wash.
Roll the other half of pastry dough into a rectangle, about 9×18-inches. Drape over a rolling pin and unroll over the filling to cover. Seal the edges by pressing down hard with the back of a fork or use your fingertips or a pastry crimper to pinch the edges into narrow pleats.
Cut out a 1-inch circle from the center of the dough. If you like you may gather any remaining pastry scraps into a ball, roll them out again, and with a cookie cutter or
small, sharp knife cut out decorative shapes such as leaves or triangles and decorate the top of the loaf. Coat the entire surface of the pastry with the remaining egg wash. Place any pastry shapes on top if desired. Refrigerate for 20 minutes. Bake the kulebiaka in the center of the oven for 1 hour or until golden brown. Serve immediately accompanied by a melted butter or sour cream.