A refreshing soup for a hot day, with a little tang from buttermilk. Serve with a spinach salad and rolls for a light meal. Cook time includes overnight chilling. Use only fresh herbs in this. Plain yogurt can be substituted for the buttermilk.
In a large saucepan place all the squash. Add the onion, garlic, broth and salt and pepper; bring to a boil, cover, reduce heat and simmer for 20 to 25 minutes, or until the vegetables are very tender.
Allow to cool slightly; puree in a food processor or blender with the basil, parsley and lemon juice until smooth. Stir in the buttermilk.
Place in a container, cover and refrigerate overnight.
When ready to serve, whisk until smooth and adjust the seasoning with salt and pepper.
Serve chilled, garnished with chopped basil and parsley.