Ají Criollo

Method

1. 1Halve the ají amarillo lengthwise and scrape out the seeds and the pale ribs with a teaspoon. The ribs hold most of the heat and nearly all of the bitterness, so leaving them in gives a sauce that fights back rather than one you can spoon freely.
2. 2Boil the cleaned chillies in water for 5 minutes, drain, and repeat once in fresh water if you want the sauce mild. Two changes of water take out most of the burn while the fruity aroma stays, which is the point of the technique.
3. 3Fry the chopped onion and garlic in 2 tablespoons of the oil over medium heat for 5 to 6 minutes until translucent without colouring, then add the drained chillies and cook 3 minutes more so their raw edge cooks off.
4. 4Tip the fried base into a blender with the queso fresco, evaporated milk, the whole ají limo and the salt, and blend 1 to 2 minutes until completely smooth with no flecks of cheese left.
5. 5With the blender running at medium speed, pour in the remaining oil in a thin steady stream over about a minute. The sauce shifts from thin and dull to thick and glossy as it emulsifies; pouring faster than this splits it.
6. 6Add the huacatay and coriander leaves and pulse for 10 seconds only. Longer blending warms the leaves and dulls the sauce to a khaki colour instead of the clean yellow-green it should be.
7. 7Stir in the lime juice, check the salt and refrigerate for at least 30 minutes before serving. It is served cold, and the flavour tightens and settles as it chills.