1 c. marshmallow creme (about 2/3 of a 7-oz. jar)
2 c. miniature marshmallows (about 1/3 of a 10½-oz. bag)
Preheat the oven to 450 degrees. Fit the pastry to a 9-inch pie dish, crimp the edge decoratively and pierce the pastry all over with a fork. Bake 9 to 11 minutes, checking occasionally and piercing it again wherever it bubbles up, until it is light golden brown. Set aside.
Reduce oven temperature to 350 degrees.
In the large bowl of an electric mixer, cream the butter and sugar together for several minutes, until the mixture is light and fluffy. Add the eggs and beat until well combined. Combine the flour, cinnamon, nutmeg, ginger and salt and beat in until the mixture is smooth. Beat in the sweet potatoes, then the milk and vanilla. (Don't worry if the mixture looks a little curdled.)