Duck breast is a fabulous cut of meat for the barbecue as the rich layer of fat bastes the meat as it grills. Salsa verde is one of my favourite sauces, and its punchy flavours cut through the richness of the meat brilliantly.
Begin by marinating the duck breasts. With a sharp knife, score through the skin of each duck breast in a diamond pattern, cutting deeply through the skin but taking care not to pierce the flesh. This is essential to allow the fat render and for the skin to crisp up nicely. Lay in a shallow dish and pour over the balsamic vinegar. Season well with salt and pepper, cover a leave to marinate at room temperature for 2 hours if you have time.
Put the potatoes in a pan, cover with cold water and add a shake of salt. Bring to the boil and cook until just tender, about 15 minutes. Drain and toss in a good slug of oil and season with salt and black pepper. Thread onto metal skewers and set aside.
For the salsa verde, add the herbs, garlic and mustard to a food processor and pulse until roughly combined. Then add the capers, cornichons, anchovy fillets, lemon juice and sugar and pulse to a paste. With the motor running, pour in the rapeseed oil in a steady stream and process until you have a smooth sauce. Season with salt and freshly ground black pepper, scoop into a bowl and set aside at room temperature.
When you are ready to cook, fire up the barbecue to a medium heat. Grill the duck breasts, skin side down, until the skin is deeply bronzed and crispy (about 6-7 minutes) then turn over a grill on the other side for a further 4-5 minutes for medium rare. Cook for a further 8-10 minutes for well done. Transfer to the warming rack to rest. If the duck fat is causing the barbecue to flame too much or the duck is cooking too quickly, move the duck to one side, reduce the heat and let the flames die down, before moving back over the heat to carry on.
Once you have turned the duck over so its skin side up, start to grill the potato skewers. They will take about 10 minutes, turning regularly, until lightly and evenly charred.
To serve, scatter the rocket over a serving plate. Ease the potatoes off the skewers and scatter over the rocket. Thinly slice the duck breasts and arrange over the potatoes. Finally, drizzle over a little of the salsa verde and serve the rest alongside.