Heat the oil in a frying pan until very hot. Season the meat with salt and pepper and cook for 2 to 3 minutes on each side. Remove from the pan and leave to rest.
Boil the potatoes in salted water and drain when tender, about 15 minutes. Allow to cool and cut in half.
Crush the anchovies, garlic and salt in a pestle and mortar until you have a paste. Place in a bowl with the grated Parmesan, zest and juice of the lemon, egg yolks and the mustard. Slowly whisk the oil into this mixture until in becomes thick.
Finely chop the chives retaining some batons for garnish. Fold these and the dressing, through the potatoes.
Wash and trim the spring onions. Cook in the same pan as the steak, remove when they are coloured and begin to wilt.
Place a neat pile of potatoes in the middle of your plate. Slice the steak and lay on top and garnish with the grilled spring onions and chive batons.
«Use avocado oil to finish your dressing. This will give it richness and color.»