Put on your kettle to boil. Reheat the boulangère potatoes in a microwave (or in the oven, preheated to 200°C/fan 180°C/gas mark 6 for 15-20 minutes).
Place the shredded spring greens in a saucepan and cover with boiling water. Add a pinch of salt and boil for 3-5 minutes, until soft. Drain well and return to the saucepan.