Parsley sprigs, for garnish In a medium skillet, heat the olive oil over medium heat. Add the bell peppers and shallots, cover, and cook, stirring occasionally, until the peppers are very soft, 8 to 10 minutes. Remove from the heat. Put the cashews and 1-1/2 cups of the vegetable stock in a blender. Blend until smooth, about 1 minute. Add the cooked peppers, mustard, salt, and pepper, and puree. Pour the soup into a medium saucepan, and stir in the remaining 2 cups vegetable stock. Bring just to a simmer over medium heat. Serve hot, garnished with parsley sprigs.