Boil the vareniki in salted water over moderate heat for 5–7 minutes, or until they float to the surface. Then use a slotted spoon to transfer them to a colander. Once the water drains, place them in a pot, drizzle with melted butter, and give them a gentle shake. Remove berry-filled vareniki from the boiling water, cool them on a board, and serve with sour cream, sugar, or syrup.
Prepare the dough using a cold method if you’re not cooking the vareniki right away. Mix the flour with cold water or milk. Dough made with cold water won’t dry out as quickly.
Avoid stiff dough, which is hard to roll out and shape; make the dough soft and add flour gradually.
If you’re in a hurry and want to shape the vareniki quickly, roll the dough into a large rectangle. Place the filling in even rows about 2 inches from the edge. Cover the filling with a second layer of rolled-out dough and cut out the vareniki using a cutter.
Roll the dough scraps into a ball and put them in a plastic bag. In the morning, use the dough to make dumplings and fill them with cheese or sour cream.
