Place all ingredients for the chicken into the Instant Pot insert. Put the lid on, being sure to set the knob to “sealing.” Cook on manual setting, high pressure, for 15 minutes. Allow for a 10 minute natural pressure release.
Slow Cooker Instructions:
Place all ingredients for the chicken in the slow cooker insert. Cook on low for 6-8 hours until the meat shreds easily with a fork.
Assembling the tacos:
Remove chicken pieces from the Instant Pot or slow cooker. Shred the chickens with two forks, then transfer to a foil-lined baking sheet. Preheat your broiler to 525℉ (or the high setting), and place the top rack in the middle of the oven. Strain the mango pieces from the juices and add to the chicken. Reserve the cooking juices for the tacos. Broil the chicken and mango on the rack in the middle of the oven to crisp the meat for 6-8 minutes, stirring occasionally and watching carefully, until the edges are slightly brown and crispy.
Place chicken and mango in warm tortillas. Top with slaw and cotija cheese. Dip tacos as desired in reserved juices.
Keep leftover chicken in the fridge for up to 5 days or freeze for up to 3 months.