For the lentils, bring a saucepan of salted water to the boil and add the lentils. Simmer for 15 minutes, or until tender, then drain and place into a bowl.
Heat the butter in a saucepan and gently fry the onion for five minutes until soft but not coloured.
Add the garlic and fry for one minute.
Stir in the double cream and simmer for 3-4 minutes, or until the sauce thickens slightly.
Pour the cream mixture over the drained lentils and add the parmesan and lemon juice. Stir until the cheese has melted and season, to taste, with salt and freshly ground black pepper. Keep warm until required.
For the lamb, rub the lamb chops with olive oil and season with salt and freshly ground black pepper.
Heat a griddle pan and griddle the chops with the garlic and rosemary for five minutes on each side, or until cooked to your liking. Remove from the heat and allow to rest for five minutes.
To serve, place the lentils onto a serving plate and top with the lamb chops, garlic and rosemary.