Dice the bacon into ½-inch (1cm) cubes and start it cooking in a skillet over medium heat while you make the halušky. Remember to stir it occasionally. Cook it until it's browned, but not too crispy.
Peel the potato and finely grate it on the smallest holes of a box grater over a bowl or cutting board, saving any liquid that accumulates. Alternatively, you can grind the potato to a rough purée in a food processor (dice the potato first and grind it using a pulsing motion until you have a semi-smooth paste, but not completely smooth). You should have about ⅔ to ¾ of a cup of potato purée.
Put the potato purée and any liquid you got while grating it into a bowl. Add the flour, egg, salt, and 2 tablespoons of water into the bowl. Stir vigorously to combine it to a thick batter. It should be thick, but loose, about the consistency of a muffin batter. Add more water, 1 tablespoon at a time until the batter is thin enough to drip slowly from a spoon. If it is too thin, add a bit more flour. It will really depend on how watery the potato is and how much of it you have. Russet potatoes are drier, so you may need the full amount of water. If using regular white potatoes, you may only need 2 tablespoons of water.
Set a large pot of water on to heat up to a low boil, just past a simmer. If the water is boiling too vigorously at first, the halušky may also fall apart when cooking.
Set a spätzle maker over the pot and pile the dough on top. Use a flexible spatula to scrape the dough back and forth over the simmering water, so it drops through the holes in little plops. A round-holed barbecue grill pan will also work. If you don't have either, quickly drop small spoonfuls of the dough into the water to make slightly larger halušky. Stir the water to separate any dumplings that might be stuck together.
Turn up the heat to medium-high. When the water comes to a boil and the halušky float to the top, let them cook for 30 seconds, then scoop them out with a slotted spoon or straining spider into a colander to drain.
Finish cooking the halušky in batches, if necessary.
Mash the feta cheese with the cream and toss it with the hot halušky. Sprinkle with the cooked bacon bits. Drizzle with 1 to 2 tablespoons of the bacon fat, if desired.
Serve with a salad or pickles.
Cooked, drained, cooled halušky freeze well. Pop them in a ziptop bag and squeeze out the air. Freeze for up to 6 months. To use them, defrost them and reheat them in a skillet with a bit of butter. Serve with the cheese and bacon, or instead of buttered noodles with any dish or sauce.
