Place tomato sauce, coconut milk, and chicken broth in the bottom of the Instant Pot. Mix in the seasonings, garlic, and ginger. Add the sweet potatoes, onions, and chicken. make sure everything is submerged in the sauce. Top with lid and cook on high pressure for 10 minutes followed by an 8 minute natural release and then a quick release.
Take the chicken out and shred it on a cutting board into bite size chunks.
Set the Instant Pot to "saute" function. Mix the cornstarch with water and then add to the curry along with the chickpeas, and fresh spinach. Simmer for about 3 minutes or until it starts to thicken. Mix the chicken back in and then turn off.
Serve curry over rice and garnish with cilantro.
For the Slow Cooker:
Place tomato sauce, coconut milk, and chicken broth in the bottom of the slow cooker. Mix in the seasonings, garlic, and ginger. Add the sweet potatoes, onions, and chicken. Make sure everything is submerged in the sauce. Top with lid and cook on low for 4-5 hours. Remove chicken, shred and add back with cornstarch mixture, and chickpeas. Cook on high for 30-45 minutes. Stir in the spinach and let sit until wilted.