200g/7oz stripped and torn kale (weight once stripped from the stems)
1–1.25kg/2lb 4oz–2lb 12oz Kerr’s Pink, Golden Wonder or Rooster potatoes, preferably of a uniform size, scrubbed
4 spring onions, thinly sliced
salt and freshly ground black pepper
150g/5½oz unsalted butter, cubed
250ml/9fl oz full-fat milk