4ounces(1 stick) cold unsalted butter, cut into ½-inch pieces
1large egg white
1 ½cupspecan pieces
2ounces(½ stick) unsalted butter, melted
2ouncesbittersweet chocolate(55% cocoa)
1cuppacked light brown sugar
¼cupbarley malt syrup
1large egg yolk
For the crust: Stir the flour, salt, and sugar together in a large bowl. Add the butter pieces and coat with the flour mixture using a bench scraper or spatula. With a pastry blender (or your fingers), cut the butter into the flour mixture, working quickly until mostly pea-size pieces of butter remain (a few larger pieces are okay; be careful not to overblend).
Combine the water, cider vinegar, and ice in a large measuring cup or bowl. Sprinkle 2 tablespoons of the ice water mixture over the flour mixture, and mix and cut it in with a bench scraper or spatula until it is fully incorporated. Add more of the ice water mixture, 1 to 2 tablespoons at a time, using the bench scraper or your hands (or both) to mix until the dough comes together in a ball, with some dry bits remaining. Squeeze and pinch with your fingertips to bring all the dough together, sprinkling dry bits with more small drops of the ice water mixture, if necessary, to combine.
Shape the dough into a flat disc, wrap in plastic, and refrigerate for at least 1 hour, preferably overnight, to give the crust time to mellow. Wrapped tightly, the dough can be refrigerated for 3 days or frozen for 1 month.
To partially pre-bake the crust, preheat the oven to 425°F and place baking sheet on a rack on the lowest position. Roll out the dough to ⅛-inch thickness and carefully lay it into a 9-inch pie pan or dish, being careful not to stretch the dough. Trim the edges and crimp as desired. Refrigerate the crust for about 30 minutes to allow it to set. Prick all over the bottom and sides with a fork about 15 to 20 times. Line the crust with a piece of parchment paper and fill it with pie weights or dry beans. Place the pie on the preheated baking sheet and bake for 20 minutes, until the crimped edges are set but not browned.
Remove the pan and the baking sheet from the oven, lift out the parchment and the pie weights and let the crust cool for a minute. Beat together the egg white and water. Use a pastry brush to coat the bottom and sides with a thin layer of egg white glaze to moistureproof the crust. Return the pan, on the baking sheet, to the oven’s middle rack and continue baking for 3 more minutes. Remove and cool completely before filling.
For the pie: Position a rack in the center of the oven and preheat the oven to 350°F. To toast the pecans, spread them in a single layer on a rimmed baking sheet and place in the oven for 6 to 8 minutes, or until the nuts are fragrant, stirring occasionally. Set aside to cool.
Bring an inch of water to a simmer in a medium saucepan. Combine the butter and chocolate in a heatproof bowl large enough to rest on the rim of the saucepan, above the water. Melt the butter and chocolate over this double boiler, whisking occasionally until smooth. Remove from the heat. Add the brown sugar, barley malt syrup, salt, cinnamon, and ginger, and stir well. Mix in the sour cream, then the eggs and egg yolk one at a time, stirring briskly after each addition. Stir in the cooled toasted pecan pieces.
Place the pre-baked pie shell on a rimmed baking sheet and pour in the filling. Bake on the middle rack of the oven for 52 to 57 minutes, rotating 180 degrees when the edges start to set, about 35 minutes through baking (if the crust browns too quickly, tend the edges with a ring of aluminum foil). The pie is finished when the edges are set and puffed slightly and the center is slightly firm to the touch but still has some wobble (like gelatin). Be careful not to over-bake or the custard can separate; the filling will continue to cook and set after the pie is removed from the oven. Allow to cool completely on a wire rack, 2 to 3 hours. Serve slightly warm or at room temperature. The pie will keep refrigerated for 3 days or at room temperature for 2 days.