Smashed potatoes exist for the surface area. Boiling them first and then crushing them flat before they hit the oven creates ridges and torn edges that go genuinely crisp, which is something a whole roasted potato can never do.

Scallions go in at two different points and that is deliberate. The white parts cook into the potato and turn sweet, and the raw green tops go over the top at the end for the sharp, fresh bite. Chop them thin so they scatter evenly instead of landing in clumps.

Roasted Garlic Grapeseed Oil is the right fat here because its smoke point is high enough for a hot oven and its flavour survives the heat. Serve them straight out of the pan while the edges are still shattering.