Pumpkin Pie with Toffee-Walnut Topping

Crust
1½ cups all-purpose flour
1 T sugar
½ teaspoon salt
6 T (¾ stick) chilled unsalted butter, cut into ½-inch pieces
3 T chilled solid vegetable shortening, cut into ½-inch pieces
3 T (about) ice water
1 large egg yolk, beaten to blend

Filling
1 15-ounce can pure pumpkin
⅔ cup (packed) golden brown sugar
⅔ cup whipping cream
⅓ cup whole milk
2 large eggs
¼ cup sugar
1 teaspoon vanilla extract
1¼ teaspoons ground cinnamon
¾ teaspoon ground ginger
¼ teaspoon ground nutmeg
¼ teaspoon salt
1/8 teaspoon ground allspice
½ cup walnuts, toasted, chopped
⅓ cup English toffee bits (such as Skor)

For crust:
Blend flour, sugar and salt in processor. Add butter and shortening and cut in using on/off turns until mixture resembles coarse meal. Add 2 tablespoons ice water; process using on/off turns until small moist clumps form, adding more water by teaspoonfuls if dry. Gather dough into ball. Flatten into disk. Wrap in plastic; chill 30 minutes.

Position rack in bottom third of oven and preheat to 375°F. Roll out dough on floured surface to 12-inch round. Transfer dough to 9-inch-diameter pie dish. Fold overhang under, forming high-standing rim. Crimp edges decoratively. Freeze 15 minutes. Brush crust all over with yolk. Bake until crust is set but still pale, about 15 minutes. Cool slightly.

For filling:
Whisk first 12 ingredients in large bowl. Pour into crust. Bake until filling is set, about 55 minutes. Transfer to rack. Sprinkle nuts and toffee around edge of hot pie, forming border. Cool pie completely. (Can be made 6 hours ahead. Let stand at room temperature.)