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 set over medium heat, heat the oil and add the red pepper flakes. Be careful not to burn the flakes, 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. Add the mango and cook for 1 more minute.
In a separate bowl, combine the pineapple juice, vinegar, sugar, and curry powder. I use a mild yellow curry powder, but if you want it hotter go for red. Add this mixture to the pan and stir to combine. Bring the mixture to a bare simmer and reduce for about 30 minutes, stirring frequently. Season with salt and pepper to taste. Add the raisins and nuts and transfer the chutney to a bowl set over an ice bath to cool.