In a large bowl, mix together the flour and salt. In a smaller bowl, stir together the oil and egg; add to the flour mixture and stir until it’s sort of rough and shaggy looking. Pour in the hot water and stir until the dough comes together. (It should be slightly tacky, but not too sticky - if it is, add a bit more flour.) Cover with a tea towel and let rest for half an hour.
Meanwhile, stir together your mashed potatoes and Alexis de Portneuf cheese. If you like, add some cooked, crumbled bacon to the mix as well. Season with salt and pepper.
When you’re ready to make peroghies, on a lightly floured surface, roll the dough out 1/4 inch thick and cut into rounds with a glass rim or round cookie cutter. Pile a large spoonful on each round and gather the dough around it, pinching it to seal - it’s a nice, soft dough, so this is easy to do even when they look overstuffed.
Bring a large pot of salted water to a boil while you cook the bacon in a large skillet set over medium-high heat. When it’s partially cooked and the fat is rendering off, add the onion and cook until both are crisp. When the water is at a simmer, carefully drop in the peroghies, without crowding the pot too much, and cook for 5 minutes, or until they float to the surface, plus an additional minute.
Remove the peroghies with a slotted spoon, draining them well, and put them into the pan with the bacon, onion and drippings. Cook them in batches for a few minutes, until browned on both sides. Serve with sour cream. Serves 4-6.