Preheat oven to 350 degrees F.
Spread pecans on a baking sheet and bake 5 minutes until fragrant. Stir half way through cooking.
Remove from oven and set aside. Allow to cool completely.
Bake sweet potatoes 50 minutes at 425 degrees F. Cool for a few minutes. Scoop out flesh and place it in medium bowl.
Set the skins on a baking sheet.
In a medium bowl, mix 1 tablespoon butter and the brown sugar together until it is coarse crumble.
Add the cinnamon, nutmeg, ginger, salt, and half of the pecans.
Divide mixture in half. Add half of the mixture to the sweet potato flesh and fold in completely, and then add the filling back to the potato skins on the baking sheet.
To the other half of the brown sugar mixture, add 1 tablespoon butter, flour and remaining pecans. Mix until it is coarse crumble.
Top each of the sweet potatoes with the brown sugar mixture.
Top with the marshmallows.
Return to the oven and bake or broil until the marshmallows are golden brown.