In a small bowl, mash the butter and miso paste together until smooth.
Heat a frying pan until very hot. Add olive oil, then the broccoli in a single layer. Leave it undisturbed for 2-3 minutes to get proper char.. do not touch.
Flip the broccoli, add a splash of water, and steam for 1-2 minutes until water evaporates.
Drop in the miso butter and let it melt over the broccoli. Mix everything together so the stems get fully coated.
Sprinkle with chilli flakes and a little more lemon juice and olive oil.
