Anticuchos de Corazón

Method

1. 1Trim the heart down to clean dark muscle: cut away the outer fat, the valves and vessels at the top, the inner membrane and every trace of silverskin. Expect to lose around a third of the weight from 1 kg. Anything silvery left behind turns to elastic on the grill and no marinade will soften it.
2. 2Cut the trimmed heart across the grain into 3 cm cubes about 1.5 cm thick, so each piece cooks through in the two or three minutes it spends over the coals.
3. 3Whisk the ají panca paste with the crushed garlic, vinegar, cumin, oregano, half the oil, the salt and the pepper. Turn the cubes through it, cover and refrigerate 4 to 12 hours. Do not go past 12: the vinegar starts to break down the surface and the meat cooks up mealy.
4. 4Soak the bamboo skewers in cold water for 30 minutes so they do not catch fire. Thread three or four cubes onto each, flat faces outward and pieces just touching rather than compressed, since tightly packed meat steams where the pieces meet.
5. 5Boil the potatoes in salted water for 20 to 25 minutes until a knife slides out cleanly, and boil the corn for 15 minutes. Keep both warm. Set the leftover marinade aside and thin it with the remaining oil for basting.
6. 6Grill over hot charcoal with the grate about 10 cm above the coals, 2 to 3 minutes per side, brushing with the thinned marinade each time you turn. Heart is offal, so cook it to 71 °C in the centre (the USDA target for variety meats): push an instant-read thermometer into the middle of the thickest cube. At that point the edges are charred and the centre is firm and pale pink-brown with no wet red left. Take the skewers off as soon as it reads 71 °C; lean heart toughens quickly past that point.
7. 7Rest the skewers 2 minutes so the juices settle, then serve with the potato and corn and a chilli sauce on the side. Any basting marinade that touched raw meat must be boiled for 2 minutes before it goes near the plate.