Pick the leaves off the coriander, and reserve for the sweet potato mash.
Finely chop the stalks.
Mix together the ground cumin, chopped coriander stalks, harissa paste, salt, pepper and olive oil, and massage the marinade thouroughly into the chicken.
Set aside until ready to cook.
Heat a pan on medium high, and sear the chicken thighs on all sides until well browned. The pan can be transferred to a hot oven to finish off the cooking if necessary. (160'C for 45 minutes is ideal, but 20 minutes at 180'C will do if you are in a hurry.)
Peel and coarsely chop the sweet potatoes.
Place in a pan of cold, salted water, and bring up to the boil. Cook until soft, about 12-15 minutes.
Meanwhile, toast the ground coriander until lightly browned and fragrant.
Peel the ginger with a spoon, and grate finely.
Combine the ginger, toasted ground coriander and butter.
When the sweet potatoes are cooked, drain, and return to the pan. Mash until desired smoothness, and stir in the seasoned butter. Adjust the seasoning.
Coarsely chop the coriander leaves, and fold into the mashed potatoes.
After removing the chicken from the oven, squeeze the lemon juice over the top and allow to rest for 5 minutes, add the olive oil and swirl the juices around the pan to amalgamate.
Wash, drain and if necessary pick the rocket leaves.
Spoon a generous dollop of sweet potato mash, and position the chicken thighs on top. Drizzle with any remaining pan juices an d sprinkle the rocket leaves on top.
«You can use any firm white fish instead of the chicken, or even a firm cheese -such as feta or halloumi- for a vegetarian version. Marinating overnight will intensify the flavours.»