Greek island salad with chicken & avocado

INGREDIENTS

• 3 spring onions
• 1.8kg roasted chicken , at room temperature
• 2 hearts romaine lettuces
• 4 tomatoes
• 2 ripe avocados
• 3 tbsp lemon juice , plus extra for squeezing
• 200g packet feta cheese
• ½ tsp dried oregano
• ½ tsp dried mint
• half a bunch of flatleaf parsley
• 5 tbsp extra-virgin olive oil
• 2 tbsp black kalamata olives
• pitta bread , to serve (optional)