Quickly cook the shrimp: Bring a large pan of salted water to a rolling boil. Drop in the raw prawns and cook for just 1-2 minutes. You'll know they're done when they turn from a translucent grey-blue to a firm, opaque pink and white, and they'll curl slightly. Immediately drain them and plunge them into a bowl of ice water to stop the cooking process. This keeps them perfectly tender, not rubbery.

Chop and prep the shrimp: Once the prawns are cold, drain them well and pat them dry with kitchen paper. Chop them into bite-sized pieces – you want them small enough to fit easily on a tortilla chip but large enough to still feel substantial. The texture should be snappy and juicy.

Marinate in citrus: Place the chopped shrimp in a non-reactive bowl (glass or ceramic is perfect). Pour the fresh lime juice over them, ensuring all the pieces are submerged. Give it a gentle stir, then cover and place in the fridge for 15-20 minutes. During this time, the acid in the lime juice will "cook" the outside of the shrimp, firming up the flesh and infusing it with bright, tangy flavour. You'll see the shrimp become more opaque.

Prepare the vegetables: While the shrimp is marinating, prepare your vegetables. Finely dice the tomato, cucumber, and red onion. The finer the dice, the better the flavours meld together. The cucumber should release a little water when you chop it, which adds to the refreshing juice of the ceviche.

Combine the base: After the shrimp has marinated, drain off about half of the lime juice – you don't want the ceviche to be swimming in liquid. Add the diced tomato, cucumber, red onion, and chopped chilli to the bowl with the shrimp. Stir everything together gently. The smell at this point is incredibly fresh and zesty.

Add the final touches: Gently fold in the chopped coriander and the diced avocado. The avocado should remain in distinct chunks, adding a lovely creamy contrast to the acidic, crunchy vegetables. Season generously with salt and freshly ground black pepper. If you're using the orange juice for a hint of sweetness, stir that in now.

Chill and serve: Cover the bowl and place it back in the fridge for another 10-15 minutes. This final chill allows all the flavours to marry together beautifully. The colour should be a vibrant mix of pink shrimp, red tomato, green cucumber and coriander, and pale green avocado. Serve immediately, while it's still cold and crisp.