The habanero peppers can be roasted on a gas stove top or in an oven. Before roasting the peppers, turn on the kitchen or stove exhaust fan.
To roast the peppers on a gas stove top, soak 3 wooden skewers in water until saturated. Skewer 1 pepper and hold over a medium-high flame. Slowly rotate the pepper over the flame until the skin is blackened and blistered. Repeat with the remaining peppers and skewers. After each pepper is roasted place in plastic bag covered with a dish towel to steam, which will help to remove the skins.
To roast the peppers in the oven, place an oven rack in the highest position and preheat the broiler. Put the peppers on a cookie sheet and place under the broiler. Using long handled metal tongs to rotate the peppers and broil until the skin is blackened and blistered. After each pepper is roasted place in plastic bag covered with a dish towel to steam, which will help to remove the skins.
Wearing gloves, remove skin, the veins, and the seeds from the habaneros. (When removing the skins, it's important to wear double layer of latex gloves or else your hands burn.)
To make the paste, blend the habaneros with the sugar using a mortar and pestle or a food processor (the latter is much faster).
Combine the habanero paste into the softened vanilla ice cream and refreeze until firm but still spreadable
Assemble cake in springform pan by alternating cake, lime sorbet, cake, habanero ice cream, cake and freeze until firm (8 hours or overnight).
Garnish with powered sugar or whipped cream and sprinkles.