Preheat oven to 400°. Line a baking sheet with parchment paper.

Place the chickpeas, olive oil, cayenne pepper and salt into a small bowl. Stir to completely coat the chickpeas.

Arrange the chickpeas in an even layer on the baking sheet. Bake until crispy, about 50 minutes, rearranging them 2-3 times during baking to ensure even cooking.

While the chickpeas roast, coat the bottom of a large pot with olive oil and place it over medium heat. When the oil is hot add the onion and sauté for about 5 minutes, until soft and translucent.

Add the garlic and continue to sauté for about 1 minute more, until very fragrant.

Add 4 cups of broth to the pot, along with the cashews and potato. Raise the heat and bring the liquid to a simmer.

Lower the heat and allow it to simmer until the potato is very tender, about 20 minutes. 

While the soup simmers, prepare the kale by removing the stems and roughly chopping the leaves.

Remove the pot with the cashew mixture from heat. Transfer the soup to a food processor bowl in batches and blend until completely smooth. Return it to the pot.

Place the pot back over medium heat and bring the liquid to a simmer. Add the kale leaves in batches, allowing each addition to simmer just until they wilt and you have enough room in the pot to add another batch. Push the leaves down with a spoon between batches.

Allow the soup to simmer until the kale is very tender, about 20 minutes.

Transfer the soup again to the food processor bowl, working in batches, and blend it to your desired smoothness. Return it to the pot.

Stir in the milk and vinegar. Thin with an additional cup of broth if desired, and season the soup with salt and pepper to taste. 

Heat the soup back up to a simmer. Remove from heat.

Ladle into bowls and top with the spicy roasted chickpeas. Serve.