Remove the cutlets from the refrigerator 1 hour before cooking.
For the purée,place 60g butter and 2 tbsp olive oil in a saucepan with a lid over a low-medium heat,and cook the onion and garlic slowly,without colouring,for 8 minutes or until soft and sweet.
Add the parsnips and cook for a further 5 minutes,then add the stock and simmer for 30-45 minutes or until most of the liquid has evaporated.
Season well,then blend to a smooth purée,adding more butter,if necessary.
Add lemon juice to your liking.
Set aside and keep warm.
For the marinade,use a mortar and pestle to pound the garlic and salt to a paste.
Add the herbs and pound for about 2 minutes.
Add the cumin,chilli flakes and 1/4 cup olive oil and stir until completely incorporated.
Mix the cutlets with the marinade and leave for 1 hour to infuse.
Preheat a barbecue.
When hot,place the cutlets on the hottest part.
Cook for 2 minutes on 1 side,then turn over and cook for a further 1-2 minutes,or until done to your liking.
Transfer to a plate,cover with foil and set aside to rest in a warm place.
Place 3 lamb cutlets on each plate.
Mix a little extra olive oil with the juices from the resting plate,and pour over the cutlets.
Give a good grind of fresh pepper.
Place a spoonful of parsnip purée on each plate (or serve it in a bowl in the middle of the table).
Finish with lemon wedges on the side.