Soak cashews in boiling water for one hour. Drain & set aside.
In a medium soup pot, cook onions in oil over medium-low heat until soft.
Add vegetable broth, potatoes, frozen peas, and cayenne pepper. Bring to a boil.
When the potatoes and peas are soft (30 – 45 minutes), turn off the heat. Cool for about 10 minutes and then place everything into a blender along with the cashews and fresh mint. Pulse until smooth and creamy. Return to pot. Add more broth or water if too thick.
Before serving, stir in fresh lemon juice, salt and pepper to taste.
Garnish with finely chopped mint leaves, croutons, and vegan sour cream, if desired.