Buy your rack of lamb already “Frenched”, meaning the last piece of the bone has been cleaned by the butcher. Also, buy your racks with 6 bones maximum to ensure even cooking throughout.
Combine the mustard and garlic and spread over and into the meaty parts of the racks. Sprinkle with the herbs and season to taste. Place in a baking dish with the meaty side facing uppermost and sprinkle with olive oil. Lightly wrap the exposed bones in tin foil and set aside until ready to cook.
Trim and cut the mushrooms to be more or less the same size, leaving the smaller ones whole. Heat some olive oil in a frying pan and cook the mushrooms and the whole garlic cloves in two batches. Add the stock and bring to a boil. Cook on a high heat until the sauce is reduced and slightly thickened. Stir in the butter. Fish out the garlic cloves (if you want to) and season to taste. Set aside until required.
When ready to serve, roast the meat in an oven preheated to 200º C for 6 minutes, then lower the heat to 160º C and cook for a further 7 – 10 minutes or until done to your liking. Remove from the oven, cover loosely with foil and allow to rest for 5 minutes. Meanwhile, gently reheat the mushroom sauté.
To serve, slice in between the rack bones to have individual chops and serve 2 – 3 chops per person on top of the mushrooms sauté.
Serves 4 – 6.