Preheat oven to 350 degrees. Whisk together milk, sugar, flour, and salt in a medium saucepan. Bring to a boil over medium heat, whisking constantly. Transfer mixture to a large bowl and whisk in molasses, butter, pie spice and vanilla. Allow mixture to cool at least 15 minutes and then whisk in egg yolks.

Prepare ten 7-ounce ramekins, greasing with butter and sprinkling with sugar to coat (this will help the souffle rise), and shake out any excess.

Beat egg whites and cream of tartar until stiff peaks form. Fold 1/3 of egg white mixture into the milk mixture until it's well incorporated. Repeat with remaining 2/3 egg whites. Spoon batter into prepared ramekins, leaving a 3/4-inch headspace on each ramekin.

Bake at 350 degrees for 25 minutes or until puffy and set. Garnish and serve immediately.