DOUGH
Place flour in a large bowl. Add eggs, oil, salt, and 1 ½ cups of the water. Mix well to form a dough, adding more water if needed.

Knead the dough on a flat surface until smooth and pliable, about 4-5 minutes

Cover with plastic wrap and allow the dough to rest at room temperature for at least 30 minutes or up to 1 hour.

FILLING
Peel the potatoes and cut into 2-inch cubes. Place in a large pot of salted water and bring to a boil. Cook the potatoes for 15 minutes or until tender.

While the potatoes are cooking, heat 2 tablespoons butter in a medium skillet over medium-low heat. Add onions and cook until tender without browning.

Once potatoes are cooked, place in a large bowl and mash. Add onions, cheese, and remaining butter. Continue mashing until the potatoes are very smooth.

ASSEMBLY
Using half of the dough, roll it out ⅛"thick. Cut out circles of dough using a 3" cookie or biscuit cutter.

Scoop 1 ½ tablespoons of filling and roll into a ball, place on the pierogi dough. Fold the dough over to form a semi-circle and pinch the edges closed. Place on a baking sheet. Repeat.

COOK
Heat 3 tablespoons butter in a large skillet. Add sliced onions and cook on medium-low heat until tender. Remove onions from the pan and set aside for serving

Bring a large pot of salted water to a boil. Gently add pierogies and cook until they float, about 2-4 minutes. Remove with a slotted spoon.

Transfer pierogies to a hot skillet (adding more butter if needed) and cook until browned on each side, about 5 minutes. Serve with onions and sour cream