Beat eggs in a large bowl.

Add oil to the beaten eggs and mix well.

In the same bowl, combine flour, cooked cold mashed potatoes, and salt.

Mix all ingredients together until a soft dough forms.

Cover the bowl and let the dough stand for 30 minutes.

Prepare your choice of pierogi filling.

Roll out the dough and cut out circles for pierogies.

Place a spoonful of filling in the center of each dough circle.

Fold the dough over and crimp the edges to seal, forming the pierogies.

Boil pierogies until they float, then pan fry with butter to a golden brown.