Prepare the avocado mayonnaise
In a bowl or mortar, whisk the egg yolks until smooth.
Gradually add the mashed avocado while mixing quickly to create a creamy texture.
Season with sea salt and a squeeze of fresh lemon juice.
Fold the shredded chicken into the avocado mixture until evenly coated.
Toast the bread
Lightly toast the farmhouse bread slices until golden and crisp.
Assemble the sandwich
Place the rocket leaves on one slice of toasted bread.
Spread the chicken avocado mixture generously over the rocket.
Add freshly ground black pepper.
Top with thin slices of red onion.
Place the second slice of bread on top and press gently.
Slice the Chicken and Avocado Sandwich in half and serve immediately.