Cut the mango flesh away from the pit. The pit is shaped similar to an obelisk, so you'll end up with 2 large pieces and 2 smaller pieces from each mango. Roughly chop the flesh.
In a saute pan heat the oil and add the chile flakes. Be careful not to burn the chile, just toast to flavor the oil. Add the onions and sweat until soft. Add the ginger and bell pepper and saute for 1 to 2 minutes. Finally add the mango and cook for 1 more minute.
In a separate bowl, combine the pineapple juice, vinegar, sugar, and curry powder. Add this mixture to the pan. Stir to combine. Bring the mixture to a bare simmer and reduce for about 30 minutes, stirring frequently. Season with salt and pepper. Add the raisins and the nuts and transfer to another container over an ice bath. I used a mild yellow curry powder, but if you want it hotter go for red.
Recipe courtesy of Alton Brown