Pre-heat oven to 350 degrees. Grease an 8x8 or 9x9 baking dish.
Peel and grate sweet potatoes into a bowl and set aside.
In a large bowl, whisk together eggs, milk, light brown sugar, molasses (if using), vanilla, butter, cinnamon, nutmeg and salt, until well combined.
Fold in the sweet potatoes and mix until the custard mixture is fully coating the sweet potatoes.
Pour in the sweet potato mixture into the pre-greased baking dish and smooth out into an even layer.
Cover with aluminum foil and bake for 35 to 45 minutes, or until the pone is just set in the middle. If it's still wet in the middle, continue to bake for another 10 to 15 minutes.
Then remove the foil and bake until the pone starts to caramelize and brown around the edges.
Remove from oven and cool for 30 minutes.
Serve with a dollop of whipped cream or scoop of vanilla ice cream.
Store leftovers, covered, in the refrigerator.