Make the Cashew Cream:
Rinse 2 cups of whole raw cashews in cold water several times. Put them in a bowl and cover with cold water. Cover the bowl and refrigerate overnight, ( or longer if you have a regular blender.)
Drain the cashews and rinse again. Place in a high-speed blender with enough fresh cold water to cover them by 1 inch. Blend on high speed for several minutes, until very smooth. Strain if the cream is not completely smooth. Refrigerate until ready to use.
Make the bisque:
In a soup pot, over medium flame, heat the oil briefly. Before it gets too hot, stir in the minced garlic. Cook and stir a minute or so, then add the diced carrots and celery. Cook and stir 5 to 8 minutes, until the carrots and celery have softened.
Add the paprika, stirring it in until the vegetables are well coated. Add 5 cups of the vegetable broth, the bay leaf and the diced yams.
Bring to a simmer, cover and cook until the yams are very tender, 20 to 30 minutes. Remove the bay leaf. Puree with an immersion blender. Or, working in batches, pour the soup onto a blender and blend until smooth. (Beware, hot soup tries to burst the blender lid off, creating a huge kitchen counter mess and potential personal burns.)
With the pureed soup in the pot, stir in the cashew cream. If you prefer a thinner soup, stir in the last cup of vegetable broth. Heat through.
Season with lemon juice, cayenne, and salt, if needed.
Ladle into bowls and garnish with the green chives and chive blossoms, if using..