This pierogi filling is delicious and it can be varied by utilizing a variety of mushrooms. If I am making this with only a single type of mushroom, I prefer the button mushroom. If I use a variety, I typically use shitake, button, and portabella (those are the easiest to find in my location). Go ahead and experiment with different types!
Beat the eggs and add the salt together in a large mixing bowl.
Add sour cream and softened butter, mix into the eggs until smooth.
Add the flour, 1 cup at a time, kneading it until the dough is pliable. The dough should be slightly gooey.
Knead the dough on a lightly floured surface until firm and smooth, add a small amount of flour as required to get a smooth texture.
Cover the dough and set aside while the filling is prepared.
Prepare the filling by melting 2 tablespoons of butter in a saute pan, then season (with salt and pepper) and cook the garlic and scallions over medium low heat until the they are softened, about 2-3 minutes.
Add the mushrooms to the onions and season with the remaining salt and pepper. Add white cooking wine and springs of thyme, then continue to heat on medium heat until the wine is reduced by half, about 5 mintues.
Stir in the cream and simmer on medium low for 3-5 minues. Remove from heat. Remove the sprigs of thyme and discard.
Flour the table. Divide the dough in half, then roll out one half to 1/8 inch thickness. Cut into 3 inch rounds using a circle cutter.
Spoon filling onto each circle and then fold each one in half, pinching the edges to seal the pierogi. If the pierogi does not seal, use a few drops of water along the edges to help the pierogi seal.
Drop each completed pierogi into the boiling water for about 3 to 5 minutes. They should float to the top when done. Remove to a colander to drain. Do NOT overcrowd your pot.
In a frying pan melt some butter, and fry each side of the pierogi, until browned. It will take about 4 tablespoons of butter to cook all 20 pierogi.