Preheat oven to 450°F.

Mix the brown sugar, butter, and flour in a small bowl until well blended.

Spread in the bottom of the pie shell.

Using an electric mixer on medium speed, beat the heavy cream, vanilla, and egg until well blended.

Pour over the brown sugar mixture.

Sprinkle with nutmeg.

Bake for 10 minutes.

Reduce the oven temperature to 350°F.

Bake for 25 to 30 minutes longer, or until a knife inserted in the center comes out clean.

Cool for at least 1 hour at room temperature.

Refrigerate until serving.