Preheat the oven to 180°C, fan oven 160°C, Gas Mark 4.

Grease and line a rectangular baking tin measuring approximately 25cm x 20cm.

Melt the chocolate and butter together in a large heatproof bowl positioned over a saucepan of gently simmering water, ensuring the bottom of the bowl doesn't touch the water.

Meanwhile, mash the Peruvian Hass avocado to a smooth puree using a fork.

Whisk the eggs and sugar together for 2-3 minutes until light and airy, then add the Peruvian Hass avocado puree and whisk again until smooth.

Sieve the flour and salt together and then fold into the mixture, you may have to do this in two batches.

Pour the mixture into the prepared tin and bake for 25 minutes in the centre of the oven.

Cool, then cut into 12 pieces.