UKRAINIAN MUSHROOM AND ONION DUMPLINGS

Steps:

• Make filling: place dried mushrooms in a small bowl and add 1/4 cup boiling water. Let soften, about 10 minutes. Strain, reserving liquid and mushrooms separately.
• In a large skillet, heat oil over medium heat. Add onion and cook, stirring often, until golden but not brown, about 5 minutes. Add button mushrooms and cook, stirring, until mushrooms have released their liquid, about 10 minutes. Sprinkle with salt and pepper and drain liquor. In a food processor, combine both kinds of mushrooms. Spoon in porcini liquid, leaving behind any silt in bottom of bowl. Pulse together until finely ground but not pasty: about 3 or 4 pulses. Add salt and pepper to taste and set aside.
• Make dough: In a small bowl, combine egg yolk, oil and 1 1/2 cups lukewarm water and whisk 1 minute. Place flour in a large bowl and make a well in center. Add a third of the egg mixture and lightly mix in with fingers or a fork. Repeat 2 more times. Using hands, fold dough together until soft: if crumbly, gently work in more water; if sticky, add flour. Transfer to a lightly floured board and knead 3 minutes. Form into a ball, transfer to a bowl and refrigerate 45 minutes.
• Lightly flour a work surface and a pan or board for the finished dumplings. Divide dough into 3 sections. Using a well-floured rolling pin, roll each section out until very thin and in a rough rectangle. Use tip of a sharp knife to cut dough into 1 1/2-inch squares.
• Drain any excess liquid from filling. Place 1/2 teaspoon filling in center of each square. Fold squares in half to form triangles, sealing filling inside. (If dough is becoming dry, lightly moisten fingertips to seal.) Pinch the 2 opposing corners together to seal tightly. Place on floured surface: do not stack. Repeat with remaining dough and filling.
• In a large pot of salted boiling water, cook dumplings until they float, 2 to 4 minutes. Drain and serve in hot borscht, or just with sour cream.