Cut the bass into dice and place in a bowl with the red onion, chillies, tomatoes, lime zest and juice.
Season with salt and add the chopped coriander.
Toss well to mix, then cover and leave to cure in the fridge for 10 minutes.
Just before serving, halve, peel and stone the avocados, then cut into dice, the same size as the bass pieces.
Toss the avocado through the bass mixture.
Taste for seasoning and add more salt if needed.
Divide the ceviche between 4 plates.
Top with a dollop of soured cream and add a drizzle of olive oil to each plate.
Serve with lime wedges.
