For the dough:
4 cups flour (480 grams) all-purpose flour, plus more for rolling the dough
250 grams water, about 1 cup plus 2 ½ tablespoons
3 tablespoons butter
1 teaspoon salt
For the filling:
1 large yellow onion, cut into thin strips (julienned)
2½ tablespoons butter, divided
1 pound Yukon Gold potatoes
¼ cup heavy cream
¾ teaspoon salt
½ cup cottage cheese
For filling and cooking:
1 egg, whisked with 1 tablespoon of water
For the dough: Stir together the flour and salt in the bowl of a stand mixer fitted with a dough hook.
In a small pot, combine the water and butter and heat until the butter is melted. The mixture should be hot but not boiling, when the water starts to steam, it’s ready. Add the water mixture to the bowl. Knead the dough for about 5 minutes. The dough should become smooth and elastic. If the dough is too dry, add a splash of water. Add a tablespoon or so of flour if the dough is too dry. Wrap the dough in plastic foil and let it rest for 30 minutes.
Make the filling while the dough rests. Cook the onions in 2 tablespoons of butter over low heat, stirring often, until caramelized. Season with salt and pepper and set aside.
Cook the potatoes in lightly salted water until tender. Drain. Heat the remaining ½ tablespoon butter and heavy cream together in the pot you made the potatoes in. Use a potato ricer and smash the potatoes over the pot with the cream. Stir to mix and season with salt and pepper. Transfer the potatoes to a bowl. Stir about ¼ cup of caramelized onions into the mashed potatoes. Stir in the cottage cheese. Season with salt and pepper, if needed. Set aside to cool while you roll out the dough.
Start by dividing the dough in four parts. Work with one portion of the dough at a time, keeping the remaining dough wrapped.
Lightly flour your work surface and roll out your dough to about ⅛-inch thickness. Use a round pastry cutter that’s about 2.5-3 inches to cut dough rounds. Fill each round with a small spoonful of filling, about 1-2 teaspoons worth. Use your finger to brush the edge with egg wash. Fold over the dough to create a half-moon. Seal the dough with a mini pierogi /empanada press or use a fork.
Transfer pierogies to a baking sheet lined with parchment paper and keep covered with a clean towel while you work.
To cook the pierogies: bring a pot of salted water to a boil. Working in batches, cook the pierogies for 1-2 minutes, they will float when they are done. While they cook, heat a sauté pan with 1 tablespoon of oil and 1 tablespoon butter until the butter foams. Remove the pierogies from the water using a slotted spoon and place directly into the sauté pan. Caramelize for a minute and toss in the remaining caramelized onions. Season with a little salt before serving.
Serve with your favorite topping. I recommend sour cream and thinly sliced chives.
For freezing: place the pierogies in a large freeze-able container and try not to stack them. Seal, label and freeze for up to 60 days. When defrosting, leave them on your counter for about 20 minutes and when they begin softening you can begin removing them from the container and cook immediately.