For the mango sauce: Combine the onions, pepper flakes, garlic, celery, mango, habanero pepper and 1 cup water in a blender and puree. Pour the mixture into a large saucepan and add the sugar, salt and lemon juice. Simmer for 10 minutes.
For the sliders: Brush the chicken with 1/4 cup of the mango sauce and sprinkle with the salt and black pepper. Let marinate in the refrigerator for at least 1 hour. Preheat the oven to 375 degrees F. Spray a baking sheet with nonstick cooking oil.
Place the chicken on the prepared baking sheet and discard the used marinade. Bake until the chicken reaches an internal temperature of 160 degrees F, measured with a meat thermometer, 35 to 40 minutes.
Pour the chicken stock into a clean bowl. When the chicken is cool enough to handle, remove the skin, and then remove the meat from the bones and shred into the chicken stock (you should end up with about 1 1/2 pounds of shredded chicken). Add 1/4 cup more of the mango sauce and toss the shredded chicken until well coated. Reserve any remaining mango sauce for another use.
Place one slice each of tomato and lettuce on the slider buns. Top each with 2 ounces of chicken and 1 tablespoon blue cheese.