In a large bowl, mix together your flour, salt and baking powder. In a small bowl beat your eggs with the sour cream and 1/2 cup water. Add wet mixture to dry and mix your dough until it comes together adding more water as needed.
Knead the dough on a lightly floured surface until firm and smooth. Cover with plastic wrap and let rest for 15 minutes.
Divide the dough into 4 portions keeping each piece under plastic wrap until ready to use.
Take first portion and form with hands into a log continuing to shape until approximately 12 inches long. With sharp knife cut into 1/2 pieces.
Take each piece (this was always my job) dip in flour and flattened into a circle using your thumb and first two fingers.
Using a floured rolling pin (and floured surface) try to roll out each piece of dough into a circle shape. Do not worry if the shape is not perfect...it all tastes the same.
OR you can roll out a section of dough and use a cookie cutter, or glass rim to cut out round shapes.
Once all pieces have been rolled out, place half a plum in the centre of each round, 1/4 tsp of sugar and sprinkle of cinnamon.
Moisten the edges with water, fold over, and press together to seal. At this point you can use a fork to seal the dough. I was taught how to flute the dough edge by pinching the edges. Place pierogi's on a floured board or cookie sheet and cover with a slightly damp dish towel. Repeat procedure with the remaining dough and plums.
In a pot of boiling water, gently drop in your pierogi's and boil in batches for about 2-3 minutes. Gently remove with a slotted spoon and place on a platter or casserole dish. Pour some melted butter over top to prevent sticking while you cook the remaining pierogi's.
Serve with sour cream & more cinnamon (if you wish) while still hot.
