Wash the green mangoes, remove the stems, and cut them into long pieces, including through the seed (referred to as "bone" in Trinidad and Tobago). Rinse and drain well.
Heat oil in a wide deep pan over medium heat. Add onion, habanero, garlic, and cumin seeds. Cook on low for 3 minutes.
Stir in Caribbean green seasoning and cook for 2 minutes more. If you'd like to make a small batch of the green seasoning, << click here. Add the curry powder, mix well, and cook until the mixture is darker and has begun to clump, about 3 minutes, allowing the spices to develop fully. If you are making this dish as part of your gluten-free diet, please read the label of the curry powder (if you don't make your own) you use, as some may have fillers that could be made from gluten.
Increase heat to medium-high and add mango pieces. Stir well to coat with the curry base.
Add brown sugar, anchar masala, salt, and water. Bring to a boil, then reduce heat and simmer with the lid slightly ajar for 20 minutes.
Remove the lid and continue cooking for 10 minutes, or until sauce is thickened and mango is tender.
Taste and adjust seasoning with additional salt or sugar if needed. Serve warm with roti or as a side dish. If it's a bit tart, you can add a bit more sugar and/or salt to help balance the flavors.
