In a medium-sized pot, add the cubed sweet potatoes and enough water to cover the cubes. Bring the water to a boil and continue boiling until the sweet potatoes are soft, approximately 8 to 10 minutes.
Drain the sweet potatoes from the water, then place them back in the pot. Add the chipotle peppers, adobo sauce, butter, milk, and brown sugar. Using a masher or a large fork, mash the sweet potatoes with the other ingredients until smooth and combined.
Add salt and pepper to taste, then serve.
Like things extra spicy? Use two chipotle peppers instead of one. Remove the additional tablespoon of adobo sauce.