Directions:

• Start by making the filling so it has time to cool. Cook the potatoes in boiling water (covering potatoes by an inch), seasoned with 1 Tbsp of salt. Drain and beat in the cream cheese, butter, salt, and pepper. Transfer to a large enough dish to cool quickly. Keep refrigerated.
  
• To Make Pierogi Dough: whisk the dry ingredients first (flour, salt, and baking powder); add the wet (sour cream and eggs) and knead until smooth. I added 2 more tablespoons of flour when kneading. Cover and allow the dough to rest for 20 minutes.
  
• Shaping: roll the dough out to an 18-inch circle and cut the dough into circles using a 3-inch glass or dough cutter.
  
• Filling: Place 1 tbsp of filling into the middle of each circle. Close the dough by pinching the filling in at the middle and moving to one end, seal the edges shut.
  
• Place pierogies on a floured tray and finish rolling out all the dough, reusing the scraps to roll out more dumplings.
  
• Meanwhile, Make the onion butter sauce: in a skillet, saute the onion in butter until translucent and golden brown over medium-high heat (about 5-8 minutes). 
  
• Boiling: Bring 3 liters of water to a boil. Add 1 Tbsp of salt and cook 10-12 pierogies at a time, for 5 minutes. Remove pierogies with a slotted spoon and place on a serving dish. Drizzle with onion butter sauce and serve with sour cream!