In a deep bowl, mix the salt and flour.
Mix together egg, water and oil. Stir this into flour mixture. Add a bit more water if you need to, but try to keep the dough adding up to 2 tbsp more water if needed to make soft but not sticky dough.
Let this sit for about 5min, and then knead until smooth, about 10 times. I’ve found having extra flour is a great to help with this. When you have a smooth dough, place back in a bowl and cover with a towel. Let it rest for about 20-30min.
Put the potato into a large pot of salted boiling water. Cook until a piece will break apart easily (mashing stage!). Mash well, but use a ricer if you have one for a smoother consistency.
In frying pan, cook the bacon. When crispy, let cool and chop. Add this to the mashed potato.
Wipe the pan out, and add the butter. When bubbling, add the onion and cook until translucent 5-6min. Add this, the cheddar and the S&P. Mix well.
Prepare 2-3 baking sheets lined with parchment paper.
Take a chunk of the rested dough and roll it out until is it ½ cm thick. Use a round cutter (about 10cm wide) to cut the dough into portions.
With each, place a little mound of filling in the centre. Close it up to look like a half moon, and pinch the edges to seal. Place this on the prepared parchment, and repeat with the remaining dough and filling.
Now, if you aren’t going to eat them right away, freeze them now. They can be cooked from frozen, so a good option.
To cook, prepare a pot with boiling salted water. Cooking a few at a time, drop the perogies into the boiling water and boil for about 4-5min. They are ready when they are floating.
Meanwhile, heat the butter in a frying pan and some of the bacon. Using a slotted spoon, take the cooked perogies and place in the pan. Don’t touch them for about 4-5min, they should have a golden crust on one side. Flip them to cook on the other side to the same crispness. Serve with sour cream and chopped chives and a bit of cooked bacon.