Prepare the shrimp: First, dice the raw shrimp into small, bite-sized pieces, about 1-2cm across. You want them to be uniform so they 'cook' evenly in the citrus. You’ll notice the raw flesh is translucent and slightly greyish-pink.

Start the 'cooking' process: Place the diced shrimp in a large, non-reactive bowl (glass or ceramic is best). Pour the fresh lime juice over the shrimp, ensuring every piece is submerged. Give it a gentle stir. The shrimp will immediately begin to change colour, turning from translucent to a firm, opaque white at the edges.

Add the aromatics: Stir in the finely diced red onion and the minced chilli. The sharpness of the onion will start to mellow as it bathes in the lime juice. Cover the bowl and place it in the refrigerator for exactly 15-20 minutes. After this time, the shrimp should be completely opaque and firm to the touch—this is the cue that it is 'cooked'. The mixture will smell intensely fresh and citrusy.

Drain the citrus mixture: Pour the contents of the bowl into a fine-mesh strainer set over a sink or a bowl. You want to discard most of the lime juice, as it can become overly bitter if left too long. Don’t worry, plenty of flavour will remain on the shrimp and onions.

Combine with the vegetables: Return the shrimp and onion mixture to the bowl. Now add the diced tomatoes, cucumber, and chopped coriander. Gently fold everything together with a rubber spatula. The colours should be vibrant: the pink-white of the shrimp against the bright red of the tomato and the fresh green of the cucumber.

Finish and season: Drizzle over the extra virgin olive oil and season with the salt and pepper. Stir gently to combine. Taste a small piece of shrimp and a bit of tomato. Adjust the salt and pepper as needed. If the lime is a little too sharp, add a tiny pinch of sugar to round out the flavours.

Fold in the avocado: Just before serving, gently fold in the diced avocado. You want to keep the avocado cubes intact for a creamy, buttery texture against the crunchy vegetables. The avocado should look bright green and fresh.

Serve immediately: Spoon the ceviche into serving bowls or onto tostadas. The final dish should look glossy, vibrant, and incredibly fresh. Serve straight away while the avocado is still perfect and the shrimp is at its peak texture.