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1
Mix flour, sugar, and salt in processor.
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2
Add butter and shortening; using on/off turns, cut in until mixture resembles coarse meal.
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3
Drizzle 3 tablespoons ice water over mixture.
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4
Process until moist clumps form, adding more ice water by teaspoonfuls if dry.
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5
Gather dough into ball; flatten into disk.
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6
Wrap in plastic; chill until firm, about 30 minutes.
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7
Roll out dough on floured surface to 14-inch round.
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8
Transfer to 9-inch-diameter glass pie dish.
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9
Fold overhang under.
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10
Crimp edges decoratively.
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11
(Crust can be made 2 days ahead.
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12
Cover; chill.)
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13
Pierce potatoes with fork.
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14
Cook in microwave on high until tender, about 6 minutes per side.
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15
Cut open; cool completely.
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16
Scrape potato flesh into bowl; mash until smooth.
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17
Measure enough potato puree to equal 1 1/2 cups.
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18
Position rack in bottom third of oven; preheat to 400F.
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19
Place puree in large bowl.
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20
Whisk in brown sugar and next 6 ingredients.
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21
Brush crust with beaten egg white.
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22
Transfer filling to crust.
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23
Bake pie until filling is puffed around edges and set in center, about 45 minutes.
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24
Transfer to rack; cool.
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25
(Can be made 1 day ahead.
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26
Cover; refrigerate.)
