01 - Place the potatoes in a pot of cold salted water. Bring to a boil and simmer for 12–15 minutes, or until fork-tender. Drain well and return to the pot to steam dry for 1–2 minutes.
02 - Mash the potatoes until smooth. Add the butter and milk; mash together until creamy. Allow to cool for 5 minutes.
03 - Stir in the scallions, flour, salt, and pepper. Mix to form a soft, non-sticky dough; add a bit more flour if needed.
04 - Lightly flour your work surface. Turn out the dough and gently knead until smooth. Flatten to about 1/2 inch thick.
05 - Cut into rounds using a 3-inch cutter or shape by hand into patties.
06 - Heat a large nonstick skillet over medium heat and add a knob of butter. Fry the potato cakes in batches, 3–4 minutes per side, until golden brown and crisp.
07 - Serve warm, with extra butter if desired.