Combine the mashed potatoes, butter and milk. Taste test and add more salt if wanted. Cool the mixture.
Add in the flour slowly, mixing into the potatoes, using just enough until the mixture comes together in a dough ball. The dough should be slightly tacky, but come together in a ball. You should be able to roll it out. Depending on how much moisture is in your potatoes, this can take varying amounts of flour. Work by feel, not amount of flour.
Using some of the remaining flour, prepare your work surface by heavily dusting it with the flour. Pinch off a 2 inch round circle of dough. Roll it out on the prepared surface until it's around 6-8 inches in diameter.
Preheat a non-stickgriddle to around 400 °F or a non-stick skillet on the stove on medium high heat. A flicked water droplet should bounce off of it when ready. Carefully lay the dough disk onto the griddle. Cook for around 60 seconds on each side, until it's browned lightly in spots.
Remove and place on a plate. Once you can touch it safely, butter it then roll into a tube. Continue to roll out the remaining dough and cook.
Serve warm or at room temperature as is, or with jams, etc.
The yield will vary depending on how much dough you use for each one.