1 chipotle chile pepper in adobo sauce, finely chopped
2 teaspoons adobo sauce
Put the sweet potatoes in a steamer basket and put the steamer in a large pot of simmering water that is 1 inch from the bottom of the basket. Cover and steam over medium-high heat for 20 minutes, or until the sweet potatoes are fork tender.
Remove the steamer basket, pour the water out of the pot and dump the sweet potatoes in the pot. Add the butter and salt and mash with a potato masher. Add the chile and sauce and continue mashing to combine. Serve immediately.