To make the roux: In a medium skillet, melt 3 tablespoons of butter over low heat. Add the olive oil then, using a wooden spoon, stir in the flour. Cook, stirring, until the mixture thickens and pulls from the sides of the pan. Remove the roux from the heat before it browns.

To make the filling: In a large skillet, melt 3 tablespoons of butter over medium heat. Add the onion and cook, stirring frequently, until the onion is soft, about 15 minutes. Add the roux to the onions then add 1 cup of chicken stock. Simmer the stock, stirring constantly, until it thickens, about 5 minutes. Add the parsley, chives, paprika and sun-dried tomatoes. Allow the sauce to return to a simmer, then stir in the sour cream. Reduce the heat to medium-low and simmer gently, stirring frequently, until the sauce reduces slightly. Season with salt and pepper and set aside to cool.

Meanwhile, season the chicken breast with salt and pepper and put it in a medium skillet. Add the remaining 2 cups of chicken stock, cover the skillet and poach the chicken over medium heat until cooked through, about 15 minutes. Uncover the skillet, raise the heat and simmer the chicken until the stock has evaporated. Allow the chicken to cool, then dice and add it to the cooled sauce. Refrigerate the filling until ready to use.

To make the pierogi: Sift the flour with the salt into a mixing bowl. In separate bowl, beat the eggs with the sour cream and 1 cup of water. Gradually stir the egg mixture into the flour mixture. Turn the dough out onto a floured board and knead it until smooth. Roll the dough out about 1/4-inch thick. Cut the dough into 3-inch rounds. Place a spoonful of filling in the center of each round. Wet the edges of the dough, then fold and seal. Bring a large pot of salted water to a simmer over medium-high heat then reduce the heat to medium. Working in batches, drop the pierogi into the simmering water and cook until they float for several minutes. Drain well and serve warm accompanied by additional sour cream if desired.