In a food processor, blend the orange zest, lemon zest, ⅓ cup mint, 3 tsp salt and ½ tsp freshly ground pepper. Rub the mint mixture all over the lamb. Cover lamb and place in the fridge for 2 hours or up to 1 day to develop the flavours.
Place the sultanas in a small heatproof bowl. Pour over enough hot water to cover. Set aside for 5 mins to soak. Drain well.
In a small bowl, whisk the honey, shallot, 2 tbs orange juice, 1 tbs lemon juice and ½ tsp salt. Stir in the oil.
Using large holes of a box grater, grate the cauliflower florets into a large bowl. (Alternatively, process cauliflower florets in a clean food processor until finely chopped.) Reserve cauliflower stem. Add sultanas, almonds, parsley and 2 tbs orange juice mixture. Toss to combine. Season with salt and pepper.
Heat a chargrill on medium-high. Using paper towel, wipe excess mint mixture off lamb. Brush all over with extra oil. Cook the lamb for 3-4 mins each side or until browned and an instant read thermometer reads 60°C for medium doneness. Set aside for 10 mins to rest.
Using a mandolin or sharp knife, thinly slice the cauliflower stem and fennel into a large bowl. Add the remaining mint and 2 tsp of the orange juice mixture. Toss to combine.
Spoon cauliflower couscous onto a serving platter. Arrange the mandarin over the cauliflower couscous and top with the lamb. Drizzle with the remaining orange juice mixture and top with the fennel mixture.
Tip: [\SERVE WITH... orange zest and lemonslices\,\SWAP ME... You can use a regular cauliflower here instead of purple cauliflower.\]