Prepare the filling: combine all the ingredients and blend in a food processor to reach a smooth consistency.
Prepare the dough:
In a large bowl, mix all the ingredients together. Once incorporated, dump the dough on a floured surface and knead with your hands.
Roll the dough into a 1mm-thick sheet and cut out circles (about 3 inches in diameter) with a cookie cutter. Place about a teaspoon of filling in the middle of each circle, and fold the dough in half, pinching the ends.
Make ahead: at this point you can freeze the dumplings. Arrange them on a floured cutting board, and leave in the freezer for about 30 minutes. After that, transfer frozen vareniki to a zip-lock bag and keep frozen for up to 3 months.
To cook: boil some water, add salt to taste. Dump the dumplings in, and cook for about 8 minute till they float up to the surface. Remove with a perforated spoon.
Traditionally served with butter and sour cream.