Regular veggie broth or chicken broth will work here – I typically use the Better Than Bouillon roasted vegetable base + water to make a broth.
I do not peel the sweet potatoes! 
It’s easier, and more fiber!
If you’re serving it right away, you can pour it directly in bowls if it’s warm enough! Or just pour it into a saucepan and heat it to your desired temp on the stovetop.
If you’re saving it for later, just go ahead and pour it right into your storage containers and pop in the fridge! Your future self will thank you!