{dough}450 g (3 3/4 cups) all purpose flour
350 g (3 sticks) unsalted butter, at room temperature
200 ml (3/4 cup) cold water
2/3 tsp. salt{mushroom filling}350 g (12 oz) mushrooms
1 medium onion
2 garlic cloves
salt, black pepper{sauerkraut filling}250 g (9 oz) sauerkraut
1 medium onion
1/3 tsp. cumin seeds (if sauerkraut is without them)
salt, black pepper{for baking}1 egg
1 tbsp. water
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