Boil the eggs until they are hard. Peel them and let them cool.
In the meantime, chop the spring onion. Use also the green of the onion. If you do not have spring onion at hand, you can alternatively take an onion and chop chives.
Cut the eggs into small pieces. Mix them with cream cheese, sour cream, mustard and lemon juice. Finally, add the spring onion. Season with salt and pepper. Stir well and you're done!