Preheat oven to 350 degrees F. Place potatoes on a foil-lined, rimmed baking sheet and bake until tender, about 1½ hours. Once cool enough to handle, remove the peels (they should just slide right off).
Add the peeled sweet potatoes to a food processor along with the brown sugar, bourbon, melted butter, salt, cinnamon, ginger, allspice, nutmeg, pepper, eggs, and pineapple. Puree the mixture until completely smooth, scraping the sides of the bowl once or twice if needed.
Transfer the sweet potato mixture to a 3-quart baking dish and bake until heated through, about 25 minutes. Remove from the oven and spread with the marshmallow creme. Put the broiler on high and return the baking dish to the oven. Broil until lightly browned, about 2 minutes.
You can use canned sweet potatoes that have been drained in place of fresh sweet potatoes. If you do this, put them straight into the food processor, no baking required. Easier, but not quite as flavorful!
You can omit the bourbon if you'd like.
The homemade marshmallow creme can be replaced with a store-bought version or even marshmallows.
You can use a kitchen torch to toast the marshmallow topping instead of broiling.