Dice bacon and add it to a pan on medium. Heat until crispy. Once cooked, use a paper towel to blot excess oil from bacon.
While your bacon is cooking, peel and slice the potatoes into 1-inch slices.
Fill a large pot with water, 1 tablespoon of salt, and potatoes. Boil potatoes until soft (about 20 minutes).
Drain potatoes and add to a bowl with salt and black pepper and mash them using a potato masher.
Add the Treasure Cave Gorgonzola and mash the cheese into the potatoes using a potato masher. Once it is fully incorporated, add bacon and stir with a spoon.
Store potato mixture in the fridge for at least 90 minutes.
To make the dough, add flour and salt to a medium-sized mixing bowl.
Put butter and water in a microwave-safe bowl and heat until the butter is melted and water is very warm. This should take about 1 minute. You do not want the water to boil.
Incorporate butter mixture into flour. Then add the whisked egg to the flour mixture. Mix the dough and then knead with your hands on a floured surface until completely smooth and then cover it with cling wrap so it does not dry out.
When potato filling has firmed up, add dough to a lightly floured surface, roll out to a thickness of one-eighth of an inch and use a 4-inch circle cutter to cut out circles. Make as many as you can, combine the scraps, roll it out again and repeat. I got around 25 circles.
Place 1-1½ tablespoon of the potato filling in the middle of the circle and fold the dough over to form a half-moon. Press to seal and make indentations with your thumb.
Boil water in a large pot, add 1 teaspoon of sea salt to the water, and add 5-10 pierogi at a time to boil. They need room to move around and you want to make sure to give it a good stir so none of them stick. Once they float, you can add them to a sauté pan on medium heat with some butter and caramelized onions to finish cooking them.