Fill a small saucepan with water up to three quarters. Add a good pinch of salt. This will prevent the eggs from cracking. Bring to a boil. Using a spoon, dip each egg in and out of the boiling water. Boil them for around 10 minutes. When done, remove from the heat and place in a bowl filled with cold water. 

Dice the eggs and finely slice the spring onion.

In a bowl, mix the diced eggs, mayo, sour cream, Dijon mustard and spring onion - leave some spring onion for garnish. Season with salt and pepper to taste.

Scoop the middle of the avocado out leaving 1/2 - 1 inch of the avocado flesh. Cut the scooped avocado into small pieces.

Place the chopped avocado into the bowl with eggs and mix until well combined. Fill each avocado half with the egg & avocado mixture and top with more spring onion.