My favorite cut of lamb with two veg. This recipe can be easily doubled.

Serves 2

lamb loin: 2 x 150-200g/5-7 oz portions
salt: a couple large pinches
mix of dried spices: 1 Tb total of mix of cumin, coriander, fennel, black pepper, etc.
mix of fresh herbs: large bunch of parsley, then smaller mix of thyme, mint, rosemary, etc. Keep the majority of the mix as parsley, otherwise the stronger herbs will overpower. Finely chop all herbs together
mustard: 2-3 Tb
olive oil: for cooking

potatoes, medium starch: 500 g/ 1 lb (Swiss Red label or any potato suited for fries)
salt: 1.5 tsp
oil: 2 Tb
butter: 2 Tb

Steam the cauliflower over the stock. Heat a pan with the stock over medium high heat, just below boiling and place the cauliflower above the liquid inside a steamer basket. Steam for 10-15 minutes or until the stem part of the cauliflower is cooked through. Remove the cauliflower and keep the stock. Steaming allows the cauliflower to retain maximum flavor and the stock will reduce to intensify flavor for the final puree.
Puree the cauliflower. Add the cauliflower, butter, salt, pepper to a food processor. Add half of the remaining stock and puree until completely smooth (3-4 minutes total), adding additional stock to desired consistency. Taste and add additional salt if desired. You can also thin further by adding additional water. Finish by squeezing in the lemon. Keep warm

Boil the potatoes. Add the potatoes to a large pot and cover with water. Bring to just under a boil and cook for 15 minutes or until the potatoes are cooked about halfway through. Drain in a sieve and allow to cool.
Chill the potatoes. Once cool, peel the potatoes and if time allows, chill in the fridge for an hour overnight.
Shred and cook. Using a grater with large holes, grate the potatoes and toss with the salt. Heat a medium sized saute pan (about 23cm/9 in) over medium heat and add the olive oil. Add the potatoes. After about 15 minutes, invert the potatoes onto a plate and slide the uncooked side back into the saute pan. Cook for another 15-20 minutes or until well browned on the bottom. In the last 10 minutes of cooking, add a few pieces of butter at the sides of the pan and allow to melt down into the potatoes.
Serve. Slide the potatoes out of the pan onto a cutting board and cut into portions.

Season the lamb. The lamb is ideally seasoned for a few hours or up to 24 hours before cooking, but can also be done just before cooking. Rub both sides of the lamb with the salt and spice mixture. If preparing in advance, wrap tightly and keep in the fridge and bring to room temperature 30-60 minutes before cooking. If seasoning just before cooking, bring the lamb out of the fridge to warm and season with the salt and spices.
Preheat an oven to 200C/400F and heat an oven proof (e.g. cast iron pan) over medium high heat on the stove top. Heat some oil and sear each side of the lamb for 2 minutes. Add the pan to the oven and roast for 8-10 minutes or until the thick part of the lamb reaches 57 C/135F for medium rare, and 60-62 C/145 F for medium. (the lamb will continue to increase internal temperature during the rest period)
Add the herb coating. Remove the lamb from the oven and spread the mustard evenly over the top side. Roll the mustard side of the lamb over the herbs to coat and allow the lamb to rest for 5-10 minutes. Cut into portions and serve with the cauliflower and potatoes.