In a bowl, combine flour and salt. Gradually add warm water while mixing until a smooth dough forms. Knead for about 5 minutes until elastic. Cover and let rest.

Peel and chop potatoes into chunks. Boil in salted water until tender, approximately 15 minutes. Drain.

In a skillet, melt butter over medium heat. Add chopped onion and sauté until golden brown (about 5 minutes).

Mash cooked potatoes in a bowl with sautéed onions; season with salt to taste.

Roll out rested dough to an eighth-inch thickness. Cut into circles about 3 inches in diameter. Place a tablespoon of filling on each circle, fold over, and pinch tightly to seal.

Boil salted water in a pot. Drop in pierogi (avoid overcrowding). Cook until they float (3-4 minutes). For added crispiness, pan-fry in butter after boiling.

Plate your pierogi and top with sour cream or crispy bacon bits before enjoying!