OK, not a traditional kulebiaka, made with salmon, rice and mushrooms-but a kasha, onion and mushroom filled one instead. The beauty of the dish is that the kasha can be made up to a day ahead. You can find the kasha filling recipe HERE.
For the Pastry:
4 cups all purpose flour
1/2 pound unsalted butter cut into small pieces
2 tablespoons chilled vegetable shortening
1 teaspoon salt
12 tablespoons ice water (plus 3-4 more if needed)
1 egg yolk
1 tablespoon cream
Into the flour and salt cut the butter and shortening until you have a fine meal. Quickly add the cold water and any extra needed to bring it together into a ball. Taking a couple tablespoons at a time, smear it against a work surface with the heel of your hand to incorporate the fats. Divide dough into two balls, wrap with plastic and chill 1 hour.
Roll out one ball into a rectangle. Mound filling in the middle leaving a 1 inch border on all sides. Top with other sheet rolled the same. Fold over and seal sides well with a fork, trying to force out as much air as possible as you go (like making ravioli). Crimp well with a fork. Use extra dough to make designs if desired. Cut a hole in the centre for steam to escape. Mix the egg yolk with the cream and brush the entire kulebiaka generously. Return to the refrigerator and chill twenty minutes.
Preheat oven to 400 degrees F.
Place kulebiaka in oven on centre rack. Bake 1 hour, rotating pan halfway through.
Serve with sour cream (and if you have them, beets).