Pierogi

In a large mixing bowl, whisk 480g spooned-and-leveled all-purpose flour and 1 tsp kosher salt to combine. Create a well in the center of the flour, add 2 lightly beaten large eggs and 180ml 40C/105F lukewarm water, then stir with a wooden spoon until a shaggy, crumbly dough forms. Turn dough out onto a lightly floured work surface and knead for 5 minutes until smooth, elastic, and no longer sticky. Wrap tightly in plastic wrap and rest at room temperature for 30 minutes to relax gluten, which prevents shrinkage when rolling.

While the dough rests, place 680g peeled, 2.5cm (1 inch) cubed Russet potatoes in a large stockpot, cover with 2 liters of cold water mixed with 1 tsp kosher salt. Bring to a rolling boil over medium-high heat, then reduce heat to medium to maintain a gentle simmer, and cook for 12-15 minutes until potatoes are completely fork-tender (a fork slides in with no resistance). Drain potatoes thoroughly in a colander, then return to the warm, dry pot to evaporate excess moisture for 1 minute over low heat.

While potatoes cook, melt 14g (1 tbsp) unsalted butter in a small skillet over medium-low heat. Add 150g finely diced yellow onion, and saute for 8 minutes, stirring occasionally, until soft and translucent with no dark browning. Mash the dried, warm potatoes until completely smooth with no lumps, then stir in the cooked onion, 225g well-drained farmer's cheese, remaining 1 tsp kosher salt, and 1/2 tsp ground black pepper. Mix until fully combined, then spread filling on a plate to cool to room temperature for 20 minutes, as warm filling causes soggy dough.

Unwrap the rested dough, divide it into 4 equal golf-ball sized portions, and keep 3 portions covered under plastic wrap while you work with one. Roll the working portion on a lightly floured surface to a uniform 3mm (1/8 inch) thickness, lifting and turning the dough often to prevent sticking. Use a floured 7.5cm (3 inch) round cookie cutter to cut clean circles from the rolled dough. Gather dough scraps only once to re-roll, as overworking re-rolled scraps makes tough wrappers, and stack cut wrappers under a damp paper towel to prevent them from drying out.

Scoop exactly 1 level tsp of cooled potato-cheese filling and place it in the direct center of each dough circle. Dip your fingertip in a small bowl of water and moisten the entire half-circle edge of the wrapper, then fold the dough over the filling to create a tight half-moon shape. Press the edges firmly together to squeeze out any trapped air, then crimp the sealed edge with the tines of a fork to create a ridged, leak-proof seal. Place assembled pierogi on a floured parchment-lined baking sheet, making sure they do not touch each other to prevent sticking.

Bring a large stockpot of heavily salted water (1 tbsp salt per 4 liters water) to a rolling boil over high heat. Add 8-10 pierogi at a time to avoid overcrowding the pot, stirring very gently immediately after adding to prevent pierogi from sticking to the pot bottom. Once pierogi float to the water surface, cook for an additional 3-4 minutes until the dough is tender. Remove cooked pierogi with a slotted spoon, drain excess water, and transfer to a lightly buttered plate.

Melt the remaining 42g (3 tbsp) unsalted butter in a large nonstick skillet over medium heat. Add boiled, drained pierogi in a single layer, working in batches if needed, and cook for 2-3 minutes per side until the exterior is golden brown and slightly crisp. Serve hot, topped with a generous dollop of sour cream, and extra sauteed onion if desired.