Spread the truffle on the outside of both the slices of bread. Place them in a hot frying pan.
Add the slices mozzarella on one slice of bread. Turn it to low heat, add a little bit of water to the pan and place a lit on it. Leave it till the mozzarella is melted nicely.
Once the mozzarella is melted, take off the lit and fry till the bread is golden brown.
Take the bread out of the pan, add the avocado to the empty slice of bread and add the basil leaves.
Close the sandwich and cut it in half.