Step 1Peel and grate the yams into a large bowl. Mix in the coconut, bananas, raisins, evaporated milk, condensed milk, butter, ginger, vanilla, lime zest and salt. Pour the mixture into a large, heavy-bottom saucepan and cook over medium heat, stirring frequently, until it comes to a strong simmer, about 30 minutes.
Step 2Heat the broiler. Pour the mixture into a buttered 8-inch square metal baking pan. Flatten the top by pressing down on it with a rubber spatula, and place it in the oven until the mixture is bruleed to a rich, dark brown color, 4 to 6 minutes. Remove from the oven and cool to room temperature, then refrigerate until cold, preferably overnight, to allow the pudding to set completely.
Step 3To serve, heat the pudding in the oven at 350 degrees until warmed through, about 15 minutes. Serve warm with a scoop of vanilla ice cream, if desired.