AROMATICS: Heat the coconut oil in a large pot over medium heat. Once melted/hot, add in the chopped onions and bell pepper. Saute, cooking occasionally until soft about 7-9 minutes. Add garlic and ginger and cook for another minute. Add in the red curry paste, coriander, curry powder, cumin, and salt to taste (I add 1 tsp fine sea salt). Cook, stirring constantly, until very fragrant, 1-3 minutes. Reduce heat slightly and add a touch more oil if anything is sticking too much.
BLEND: Add in 1 cup of the mango and cook, stirring constantly for 1 more minute. Vigorously shake the can of coconut milk and pour in the entire can. Increase the heat to high, bring to a boil, and then lower the heat to a low simmer and cook for 10-15 minutes. Meanwhile, cut the chicken into 1-inch cubes. Once the mixture has simmered, carefully transfer the sauce to a blender. Blend the sauce (Note 5) until completely smooth and then return the sauce to the pot.
COOK CHICKEN: Heat sauce over medium-low, returning it to a low simmer. Once simmering, add in the chicken, and stir through. Cover the pot with a lid and cook for 8-15 minutes. (Breast pieces are usually done around 8 minutes and thighs closer to 15 minutes -- sometimes a little longer depending on size.) Check doneness by using a meat thermometer or cutting open the largest piece of chicken you can find -- it should be white throughout.
FINISH CURRY: Once the chicken is cooked through, reduce heat to the lowest setting and stir in the remaining 1 cup mango. If using, add in chopped cilantro (we add about 1/3 cup, finely chopped), zest and juice of a lime, fish sauce, and/or kaffir lime leaves if using. Taste and adjust curry seasonings to personal preference. Add salt if needed. If it's too sweet, add a touch more fish sauce and if it's not sweet enough, add a touch of sugar -- flavors should sing! Serve curry over cooked rice and garnish plates with additional cilantro if desired. Enjoy!