Sprinkle pork with salt and pepper. Place in a 3½- or 4-quart slow cooker (see Tip).
To make a bouquet garni, cut a 6-inch square from a double thickness of cheesecloth. Place peppercorns, cumin seeds, garlic, oregano, and bay leaves in center of the cheesecloth square. Bring up corners of the cheesecloth and tie with kitchen string. Add to the slow cooker. Add broth.
Cover and cook on Low for 10 to 12 hours or on High for 4½ to 5 hours.
Using a slotted spoon, remove the meat from the slow cooker. Discard the bouquet garni and the cooking liquid. Using two forks, coarsely shred the meat; discard any fat. Sprinkle the meat with lime peel and lime juice; toss to mix. Serve atop tortillas. Top with scallions and if desired, sour cream and salsa.
Tips: To crisp the tortillas, coat both sides with cooking spray and bake in a 375°F oven for 10 minutes, turning once, until crisped and lightly brown.
For easy cleanup, line your slow cooker with a disposable slow cooker liner. Add ingredients as directed in recipe. Once your dish is finished cooking, spoon the food out of your slow cooker and simply dispose of the liner. Do not lift or transport the disposable liner with food inside.
Equipment: 3½- or 4-quart slow cooker, cheesecloth, kitchen string