If you are using whole chicken thighs, begin by boning them (discard the bones). Otherwise, unroll the thigh fillets and season the inside. Blitz the chopped chicken breast in a food processor till smooth, and then add the coriander, chilli, lime zest and juice, spices, ginger and garlic. With the food processor still running, slowly pour in the cream and season.
Flatten out the thigh fillets, skin-side down, then divide the spiced chicken mixture evenly between them, spreading it over. Roll up the thighs into a rough cylinder shape and then wrap tightly in greased foil.
To cook, poach the chicken parcels in boiling water for 15-20 minutes until the chicken is cooked through, then plunge into iced water till cool. Heat 1tbsp vegetable oil and the butter in a frying pan over a medium heat and fry the ballotines until they are browned all over.
Cut the sweet potato into 2cm cubes. Drop them into a large pan of salted gently boiling water for 5-7 minutes and poach until cooked. Plunge into iced water, then set aside.
To make the vinaigrette, heat the olive oil in a saucepan with the cardamom. Heat over a low hat for about 30 minutes but do not allow it to boil or overheat. Take the pan off the heat and allow the cardamom to infuse for as long as you can get (at least overnight in the fridge). Pass the oil through a sieve and discard the cardamom pods.
Add the vinegar, suagr and coriander to the oil and you have a wonderful cardamom-infused vinaigrette. To serve, toss the potato cubes in the vinaigrette with the rocket and place on a plate. Top with slices of the chicken - hot or cold.