Fry the brioche in a pan with butter until golden brown.
Place the eggs in a saucepan with cold water and bring to the boil. Boil the eggs for 4 minutes when the water starts to boil. Plunge the eggs into cold water and peel them.
In the meantime, cut the avocados all the way around the stone. Twist the two halves apart. Remove the stone and scoop the flesh out of the skin with a spoon. Add the lime juice and mash with a fork. Season with salt and pepper.
Spread a thick layer of mashed avocado onto the brioche. Arrange the smoked salmon on the avocado. Top with the boiled egg and garnish with the lime zest, chives, salt and pepper.
