Mix all ingredients in a large bowl until fully combined.
Pour into 9" pie plate (no crust needed).
Bake for 15 minutes.
Reduce heat to 350 F and bake for another 40-50 minutes, until a toothpick comes out dry.
Remove from oven and leave on counter for two hours before use.
Put the crustless pie in a large mixing bowl and beat it for about thirty seconds to evenly distribute any moisture.
Load pumpkin pie "frosting" into a piping bag and spread or pipe onto cooled cupcakes or cakes.
Video
Notes
As you might guess, this technique works just as well with other similar pies, like sweet potato pie.Store in the refrigerator for up to four days. Bring to room temperature before serving.