Preheat oven to 350 F. Butter 6 ramekins.
Put the mashed sweet potatoes in a large bowl. Stir in the melted butter. Add the egg yolks one at a time, beating well after each addition. Add the pineapple, rum, nutmeg, and ginger, and stir well to combine. Season to taste with salt and pepper. Divide the mixture evenly among the ramekins. Using a spatula, spread the sweet potatoes so they are even on top. Bake 15 minutes.
In a medium fry pan over medium-high heat, melt the butter. Add the remaining ingredients and stir to combine. Cook just until warmed through, about 2 minutes. Spoon the praline onto the tops of the sweet potatoes in the ramekins, dividing the evenly among them.
Using a kitchen torch, fire the praline until it bubbles vigorously. Serve immediately.
Serves 6 - 8.