Boil and peel the beetroot. Place in a food processor and blend until a smooth paste is formed. If the beetroot isn’t smooth, add water a tablespoon at a time.
Boil and peel the potatoes. Place in a bowl with the beetroot paste and mash until all lumps are gone.
Add lime juice, salt, olive oil and chilli paste. Stir until well combined. Place in the fridge until needed.
In a large bowl, create an ice bath. In a slightly smaller bowl, mix together the tempura flour and soda water. Sit the bowl in the ice bath so that the mixture remains chilled.
Clean the prawn tails, and season with salt and pepper.
In a deep pot add the vegetable oil and heat. To test if the oil is hot enough, dip the handle of a wooden spoon into the oil. When the oil is hot enough, it will bubble around the handle.
Immerse the prawn tails in the tempura mix one by one, and drop carefully into a pot with hot oil. Deep-fry for around 4 – 5 minutes.
Take out the cold potato mash from the fridge and divide into three equal parts. Form each portion into a ball using your hands and place on three separate plates. Arrange the prawn tempura on top of the potato causa. Top with avocado wedges, mayonnaise and parsley leaves.
Chef’s Tip: To make the causa more colourful, add 3–4 tablespoons of beetroot puree.