Chop the sweet potatoes into quarters or sixths and place in a full pot of water. Bring to a boil and cook 15 to 25 minutes, until sweet potatoes are soft when poked with a fork. Transfer potatoes to a cutting board and chop into large chunks once cool enough to handle.

Heat bacon over medium-high in a skillet until crispy, about 5 minutes. Leave bacon drippings in skillet and transfer bacon to a cutting board and chop.

Slowly pour the cider vinegar into the skillet with the bacon drippings. Add the mustard, garlic, and salt, and allow mixture to come to a gentle boil. Cook 2 to 3 minutes, until mixture has thickened slightly.

Add the potatoes, bacon, and green onion to a large bowl. Pour in all of the bacon-cider dressing mixture and stir well to combine. If desired, mash the potatoes to desired consistency, or leave chunky.

Let stand 10 minutes before serving.