Onion Prelude: In a heavy saucepan, gently sweat the diced onion in butter until soft and translucent, avoiding coloration.
Cool Cucumber Ballet: Add the diced cucumber to the saucepan and continue to cook gently for a further 5 minutes.
Stock Symphony: Pour in the vegetable stock and bring it to a boil.
Reduce the heat, season with salt and pepper, and simmer for 5 minutes.
Add the chopped fresh parsley and lemon juice, continuing to cook for an additional 5 minutes.
Chill Retreat: Blend or process the soup into a smooth purée.
Allow it to cool, then transfer it to the refrigerator to chill.
Creamy Crescendo: When ready to serve, whisk in the single cream to add a luxurious touch.
Serve with Sophistication: Ladle the Crisp Cucumber Elegance into chilled bowls.
Garnish with a sprig of fresh dill or cucumber slices if desired.
Serve the soup chilled.