For the coconut green onion rice: Melt the butter in a medium saucepan over high heat. Add the onion and cook until soft, about 2 minutes. Add the rice and stir to coat the grains in the butter. Add the coconut milk, salt, pepper and 1 cup of water and bring to a boil. Stir once, cover, reduce the heat to medium-low and cook until tender, about 16 minutes.
Preheat the oven to 300 degrees F.
Spread the cashews on a baking sheet and toast in the oven until lightly golden brown, about 8 minutes. Let cool and finely chop in a food processor.
Remove the rice from the heat and let sit, covered, for 5 minutes. Remove the lid, fluff the rice with a fork and fold in the green onions and half of the cashews. Let sit 5 minutes more before serving.
For the chicken curry: Heat a small saute pan over low heat. Add the allspice, cloves and fennel and toast, shaking the pan occasionally, until you can smell the spices, about 5 minutes. Remove from the heat and let cool slightly. Transfer the spices to a coffee or spice grinder and finely grind. Combine the ground spices with the curry powder in a small bowl.
Heat the oil in a large Dutch oven over medium-high heat until it begins to shimmer. Season the chicken with salt and pepper and then with 1 tablespoon of the curry spices, tapping off any excess. Brown the chicken on all sides, about 8 minutes, and remove to a plate.
Add the onion to the Dutch oven and cook until soft, about 4 minutes. Add the ginger and cook for 30 seconds, then add the remaining curry spices and cook for 1 minute. Add the tomato paste and cook for 1 minute. Add the chicken stock, coconut milk, salt and pepper and cook until reduced slightly, about 10 minutes. Add the cinnamon sticks and mango and cook until reduced slightly, about 10 minutes. Reduce the heat to low, add the chicken and cook until tender, about 15 minutes. Remove the chicken to a bowl and discard the cinnamon stick and mango pieces. Add the dried coconut and the remaining 1/2 cup cashews and cook until slightly thickened, about 10 minutes more. Remove from the heat, return the chicken to the pot and fold in the green onions, cilantro and mint and season with salt, pepper and honey, if needed.
To serve: Spoon the rice into bowls and ladle some chicken curry over.