Combine the chicken, yoghurt, mustard, dill and lemon juice. Season with salt and pepper.
Divide the mixture evenly between the bread slices on a baking tray. Scatter over the mozzarella. Cook under a hot grill for about 3 minutes or until mozzarella has melted.
Make avo roses by removing the avocado skins and pips. Working with 1 half at a time, place cut side down on a cutting board. Slice through the width into very thin slices.
Fan out the avocado slices into a straight line. Beginning at one end, gently roll up the slices into a spiral rose shape. Repeat with the rest. Place an avocado half on each toast. Season with salt and pepper. Serve immediately.
