Sauté the minced garlic and onion until the onions turn translucent. Add a bit of broth if they start to stick.
Add the sweet potatoes and beans and veggie broth.
Bring to a boil, then reduce it to a simmer and cook until the potatoes are tender, 10 - 20 minutes.
Remove from the heat and stir in the salt, pepper, and cayenne.
Optional: Take out one cup of soup, that will not be blended, to keep a little texture to the soup.
With an immersion blender, puree the soup until silky smooth. If you do not have one, allow it to cool until you can transfer it to a blender to blend.
Add back in the chunky cup that you kept out previously, optionally.
Serve the bisque garnished with the pepitas and a drizzle of yogurt.