Causa puno – purple potato, tuna and rocoto pepper causa

First, cook the potatoes. Leave them in their skins, put them in a large saucepan and cover them with water. Place over a high heat, bring to the boil, then cook the potatoes until just tender (about 15–20 minutes)

Whilst the potatoes are cooking, make the chilli paste. Heat the oil in a small frying pan over a low–medium heat. Fry the onion for 7–8 minutes until soft, but not browned, then add the garlic and chilli and fry for 2–3 minutes more to soften

Season with salt to taste, then allow to cool completely. When cool, blitz to a smooth paste, then set aside until needed. (You can store in an airtight container in the fridge for up to a week)

Once the potatoes are tender, remove the pan from the heat and drain. When they are cool enough to handle, peel them and mash the flesh. Add 3 tbsp of the chilli paste to the mash, along with the lime juice and olive oil and season well with salt and pepper. Allow to cool

Next make the tiger's milk. Place the ginger, garlic, coriander and lime juice in a bowl and allow to infuse for 5 minutes

Strain the juice, then add the rocoto pepper (or chilli) and the salt. Transfer the mixture to a food processor and blitz until smooth. Taste and adjust the salt and lime juice as necessary

To make the tuna tartare, whisk together 50ml of the rocoto tiger’s milk and the mayonnaise, then season with salt and pepper. Add the tuna and stir to combine, then cover and leave the tartare to chill in the fridge until you are ready to serve

To make the avocado purée, halve the avocado, remove the stone and peel the halves. Place the avocado flesh with the squeeze of lime juice and a pinch of salt in a food processor or blender and blitz until smooth

To assemble the dish, divide the potato mixture into 4 equal portions and shape each into a round patty, like a burger. Place one patty on each of 4 plates. Spoon a quarter of the avocado purée on top of each patty, then top with equal portions of the tuna tartare and drizzle with a little more rocoto tiger’s milk, if you wish. Decorate with the shiso leaves and serve immediately