Section the pork shoulder into large chunks, if not already sectioned. Place the pork, garlic and onion into slow cooker. Combine all the spices in a small ramekin: salt, garlic and onion powder, cumin, paprika and sugar. Mix together thoroughly, then season the meat. Add the vinegar and broth. Close the slow cooker and cook on 'HIGH' heat for 4 hours, or 'LOW' for 6 hours. Stir once after 2 1/2 hours.

After 4 hours, remove the pork from cooking liquid and shred using two large forks; set aside and keep warm. Pour the remaining liquid into a frying pan. Bring the liquids to a simmer over medium heat and cook for 15 to 20 minutes, or until reduced in half. Pour the resulting sauce over the shredded pork. If not serving tacos right away, keep the meat warm in the slow cooker.

Prepare the mango salsa: peel and dice mango, seed and dice tomatoes, chop cilantro and shallot. Combine all the ingredients in a small bowl and add the lime juice, season with salt and a bit of olive oil to taste.

Prepare the guacamole: mash the avocados into a puree in large bowl using forks or a potato masher. Then, combine the avocado with lime juice, salt, garlic, olive oil, cilantro and sour cream. Mix until creamy.

For serving the tacos, I recommend toasting or grilling the taco shells. I use my gas stove top and simply place the tacos over open flames for a few minutes until they're warm and slightly charred. Alternatively, you can warm the shells in a preheated oven or under the broiler.

Spread a spoonful of guacamole over the taco shell, follow with a generous amount of pork carnitas and top with mango salsa, hot sauce and sour cream, if desired.