Slake the cornflour first. Mix it to a smooth paste with a few spoonfuls of cold water before it goes anywhere near the pan. Tipped in dry it lumps and there is no recovering it.
- Oil in the pan, dried onion three minutes until sweet-smelling.
- 400 ml water and the stock cube. Drained potatoes in, crushed roughly against the pan so some of them thicken the soup.
- Evaporated milk and drained sweetcorn in. Bring to a bare simmer: a hard boil will make it grainy.
- Cornflour paste stirred in. Two minutes until it thickens visibly.
- Off the heat, flake in the drained mackerel with plenty of black pepper. Ninety seconds in the residual heat is enough.
Pepper matters more here than in almost anything else on the site. Chowder without a lot of it tastes of nothing but milk.
Serves 4.