In a medium bowl, combine the brown sugar, allspice, cumin, cloves, cinnamon, salt, pepper, and cayenne pepper. Rinse and pat dry the chicken, then place between two sheets of plastic wrap and pound with the flat side of a meat mallet until even in thickness. Brush the chicken with the canola oil, then sprinkle with the spice rub until every breast is thickly covered.
Preheat a grill pan over medium heat. Once hot, coat with a thin layer of oil or cooking spray, then place the chicken in a single layer and cook for 5-6 minutes. Flip the chicken and continue cooking for an addition 5 minutes, or until a meat thermometer reads 165 degrees. Remove from heat, wrap each breast in aluminum foil, and allow to rest for five minutes. While the chicken is cooking, heat tortillas on a comal over medium until tortillas crisp around the edges and blacken slightly. Keep heated tortillas wrapped in a clean towel and set aside.
In a large bowl, add the mango, avocado, cabbage, cilantro, and red onion. Add the lime juice, olive oil, salt and pepper, and toss to coat. Adjust seasoning as necessary. In a small bowl, whisk together the sour cream, lime juice, and cumin. Slowly add water until mixture can be lightly drizzled. Plate tortillas with sliced chicken, top with a heaping spoon of slaw, and a drizzle of crema. Serve immediately.