In a bowl, combine flour, egg, and a pinch of salt. Add water as needed to form a dough. Knead for 5 minutes and let it rest.

Mash boiled potatoes and mix with cheddar cheese, salt, and pepper.

Roll out the dough, cut into circles, and fill with potato mixture. Fold and seal edges.

Boil pierogies for 5-7 minutes until they float.

Fry boiled pierogies in butter until golden and crispy.

Serve with sour cream and garnish with chives.