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.