Give the potatoes a scrub, if necessary, but don't peel them.
Put the spuds in a wide pan that's just large enough to hold them all in a single layer, then add the salt (don't be alarmed: you won't end up eating all of it!).
Almost, but not quite, cover with cold water.
Put a clean cloth or a large cabbage leaf on top of the potatoes, to cover them, then pop on the pan lid.
Bring to a boil, then turn down the heat and simmer for about 15-25 minutes, until cooked through.
Meanwhile, make the mojo.
Toast the cumin seeds in a dry pan until fragrant, then grind to a powder with a pinch of salt.
If using a pestle and mortar, add the garlic and pound to a paste, do the same with the chilli, then add the paprika and cayenne (start by adding just a quarter-teaspoon) and vinegar.
Gradually beat in the oil until everything's well mixed, then adjust the seasoning to taste, remembering the extreme saltiness of the potatoes.
If you have a mini chopper or stick blender, you can just whizz everything up.
Drain the potatoes and return them to the same pan over a low heat.
Cook, shaking the pan to ensure they don't stick, until coated in salt, then either serve immediately with the mojo or wrap the pan in a tea towel until you're ready to eat.
