Step 1

PreparationMake crust: Preheat oven to 350°F. Blend gingersnap crumbs, walnuts, sugar and salt in processor until walnuts are finely chopped. Add butter and process until mixture forms moist crumbs. Press crust onto bottom and up sides of 9-inch-diameter metal pie pan.

Step 2

Make filling: Purée yams in processor. Add 1/2 cup plus 2 tablespoons cream, brown sugar, egg and yolk, rum, pumpkin pie spice and salt; blend until smooth. Pour into crust. Smooth top. Place walnut halves around edges.

Step 3

Bake until filling is set in center, about 40 minutes. Cool pie on rack. Chill until cold. (Can be prepared 1 day ahead. Keep refrigerated.) Pipe or spoon sweetened whipped cream on top of pie between walnuts, if desired.