Fire up the barbecue or heat the grill to very high. Pound the garlic, chilli and sugar to a rough paste using a mortar and pestle. Stir in the olive oil and coriander leaves then season with salt and pepper. Alternatively, whizz everything together in a small food processor.
Thread the pork medallions and spring onions onto skewers, allowing three medallions per skewer. Put onto a plate, then brush the paste over both sides, being quite generous.
Barbecue the medallions for 3 minutes each side, until the meat is just cooked through and starting to caramelise. Dab any leftover paste over the pork now and then. Pork medallions are low in fat and can dry out easily, so take care not to overcook. Serve the skewers with lime wedges for squeezing.
If you want to get ahead for a barbecue for larger numbers, thread the skewers and coat in the marinade up to 1 hr before - but don't add any salt until just before you cook.
If using wooden skewers, soak them in water for at least 30 minutes before cooking.
Only meat reared to RSPCA standards gets the Freedom Food label. Find out more about Freedom Food.
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For top tips on protecting you and your family when preparing raw meat and poultry, visit Food Safety in the Home and view the full Food safety at home video.