Wash, peel, and dice sweet potatoes. Place in a steamer basket in a large pot, and add enough water to reach the bottom of the basket, but not touch the sweet potatoes. Steam for 20 minutes, or until sweet potatoes are cooked soft. Remove the potatoes from the pot, and discard the water. In the same pot, melt the butter. Add the spices, and cook, stirring, for about 30 seconds (this allows the spices to "bloom" and release their flavor more completely.) Remove from heat, and return the sweet potatoes to the pot. Stir to combine with spices, and then mash to your favorite consistency. Be sure to incorporate the spices uniformly through the potatoes. Serve piping hot! 

A note on the Chipotle: try this dish at 1/4 tsp first... a little goes a long way! Then if you want more heat, increase the amount next time you make it.  Always feel free to adjust spice quantities to suit YOUR unique palate!