Rub the lamb with oil, mustard and herbs, season with salt and pepper.
Brown the lamb on both sides over a moderate heat, then transfer to a preheated 180° C oven until cooked to your liking. (Cutlets cook more quickly – just pan grill or BBQ 2-3 minutes per side).
Cook the potatoes in boiling salted water until tender. Drain, then add a knob of butter and a little milk and mash. Season to taste.
Blanch carrots in boiling water until tender. Drain and add the oil, season with salt and pepper and sprinkle over the chives.