Place all the ingredients in a large pot and heat over medium heat. When it comes to a boil reduce the heat to low and let it simmer for 30 minutes with the lid on.
Pass the stock through a colander and keep the stock. You can make soup out of the stock's veggies. This stock will now be the liquid for our shimp or langoustine stock.
Separate the head from the tails and peel the tails. Make a shallow cut along the back of the tail and remove the vein. Reserve the tails to one side and the shells on the other side.
In the shrimp's or langoustine's head there's a black bag with sand in it that you need to discard. If you're using Peruvian shrimp there's also a bag in the head that has the coral in it and it will tint your hands red. You need to collect that for the recipe.
Rinse the heads before starting to make the stock.
Place the pot on high heat and let it heat up. Add the heads and shells to the pot and toast them for a few minutes, stirring constantly.
Add the vegetable stock, put a lid on it and decrease the heat to low. Let it simmer for 30 minutes.
Place the stock along with the heads and shells in a blender and pulse it 3-4 times to make them release more flavour. Pass it through a fine colander and discard the shells and heads
Peel the potatoes and cut them in 2cm / 0.7in thick slices. Cook the potatoes in cold water, plenty sal over medium heat. When it starts to boil reduce the heat to a slight simmer. Cook them until tender.
Cook the onion over medium heat in olive oil until it becomes translucent and smells sweet.
Add the oregano leaves but first rube them between your hands to help them release the flavour. If you're using dried oregano also do this. Sautée for a few seconds and then add the garlic. Cook it for a minute.
Add the coral and panca chilli and mix for a minute, let it thicken.
Add the stock and let it simmer until you have 2/3 of the original volume. When you try it, it should be intense and ready to eat if you wanted to.
Add the rice (need 20 minutes to cook) and stir every once in a while so it doesn't stick to the bottom.
After 15 minutes of adding the rice, go in with the tails and whole shrimps or langoustines (they only need 5 minutes to cook). After 4 minutes add the peas and the potatoes that only need one minute in the stock.
Finish with the evaporated milk and correct the level of salt and pepper.
Serve with a fried egg, toasts with queso fresco and a slice of Peruvian yellow chilli.
*Si estás en un país donde no encuentras camarones de río o el camarón está en veda (la cual siempre debemos respetar), lo que te recomiendo que hagas es un caldo más concentrado para reemplazar el coral. Pesa el doble de camarones o langostinos, pélalos y las colitas de la mitad guárdalas para otra receta pero usa las cáscaras. Así tendrás un caldo el doble de concentrado en sabor. Les juro que queda igual de increíble y les va a encantar.