For the dough: Combine flour, 1/2 teaspoon salt, and baking powder in a bowl and mix well. Add egg, sour cream, water, and canola oil and knead by hand or in a stand mixer fitted with dough hook attachment for 8 to 10 minutes.
For the potato filling: Mix together the potatoes, goat cheese, red onion, chives, salt, and pepper, to taste. Add the heavy cream as needed to adjust the consistency.
For the caramelized onions: Cook the onions with 3 tablespoons butter very slowly over low heat. Season the onions with salt, freshly ground black pepper, and chopped thyme.
For the truffe creme fraiche: Roll dough into 1/8-inch sheets and then cut 2-inch circles out of that. Place heaping tablespoon of filling onto each circle and fold into half-moon shape. Seal with beaten egg.
To serve, gently saute pierogies in olive oil, top with onions and creme fraiche.
The potatoes should have the feel of stiff mashed potatoes.
Recipe courtesy of Stanton Social