Heat oven to 400 degrees F.
Line a cookie sheet with parchment paper.
Arrange the Tartlet shells onto the cooking sheet.
Place sweet potatoes in a bowl and smash with the tines of a fork.
Stir in the maple syrup and spice then heat in microwave for 1 minute.
Fill the shells (about 2 tsp in each shell); set aside.
Whip the egg whites with the cream of tarter until glossy and fluffy.
Top sweet potato Tartlets with a generous dollop of egg white.
Bake for 2-3 minutes until egg white has turned light golden brown.