Tear the tortillas into small pieces; toss with the chiles, sesame seeds, raisins, onion, garlic and five-spice powder in a bowl. Heat a large cast-iron skillet over medium-high heat. Add the tortilla mixture; cook, stirring, until the sesame seeds are toasted and the onion is slightly charred, about 5 minutes.
Add the tomatoes and cook, stirring and scraping up any browned bits, until the liquid evaporates and the tomatoes start browning, about 6 minutes. Add the cilantro and 1 1/2 cups water; bring to a boil, scraping up the skillet. Working in batches, transfer to a blender and puree until smooth, about 4 minutes. Transfer to a 6-quart slow cooker.
Season the pork all over with salt and pepper; add to the slow cooker. Cover and cook on low, 8 hours.
Before serving, pierce the sweet potatoes several times with a fork: microwave until tender, about 8 minutes. Remove the pork from the slow cooker and slice. Top with the sauce and more sesame seeds and cilantro. Serve with the sweet potatoes and tortillas.
Photograph by Justin Walker
Courtesy of Food Network Magazine