A soup that highlights the sweet potato flavor.
Sweet potatoes: Peel the potatoes and reserve 1/4 of the skins (those will go in the soup). Cut sweet potatoes in half, then slice into 1/4 inch half-rounds.
Shallot: thinly slice
Melt butter in your favorite soup pan. Add shallots and thyme. Cook for about 5 minutes, until soft. Then add the water and bring to a simmer.
Remove the pan from the heat. Add sweet potatoes and reserved peels to the pan. Let stand, uncovered, for 20 minutes. This cooks the sweet potatoes without making them overly starchy.
Put the pot back on the stove and add the brown sugar, vinegar, 1.5 tsp salt and 1/2 tsp pepper. Bring to a simmer, then reduce the heat to low, cover, and cook until potatoes are very soft. This will take about 10 minutes.
Remove the thyme sprigs. Then puree the soup with an immersion blender, or user a regular blender for an ultra-smooth soup.
Add more liquid if needed. Season with salt and pepper if needed. Top with chives (or any other topping), if you are so inclined.