How to Make It
Prepare the crust: Whisk together white whole-wheat flour, pastry flour, milk powder, baking powder, and salt in a large bowl. Using a pastry blender or 2 knives, cut in shortening and cold butter until shortening and butter are well distributed and small clumps begin to form. Stir in 1/4 cup ice-cold water; add up to 2 more tablespoons water, 1 teaspoon at a time, stirring just until dough begins to come together. Turn dough out onto a lightly floured surface, and gently knead 1 or 2 times. Divide dough into 2 pieces. (One piece should be just slightly larger than the second, about 8 ounces for the first piece and 7 ounces for the second.) Shape each portion into a disk. Lightly flour surface, and roll slightly larger disk into a 12-inch circle; fit into a 9-inch pie plate. Trim dough to edge of pie plate. Roll remaining dough disk into an 11-inch circle. Using a pizza cutter or scalloped dough cutter, cut circle into 16 (1/2-inch-wide) strips. Weave dough strips into a lattice pattern on a parchment paper–lined baking sheet. Chill dough in pie plate and on baking sheet 45 minutes or up to 1 day.
Prepare the filling: Preheat oven to 350°F. Place goat cheese, cream cheese, egg yolk, honey, and lemon zest in a medium bowl, and beat with an electric mixer on medium speed until smooth and creamy, 1 to 2 minutes. Spread mixture in an even layer over dough in pie plate; chill until ready to use.
Arrange pear slices in a single layer on a parchment paper–lined baking sheet. Lightly coat with cooking spray. Bake at 350°F until pears start to soften and release some of their juices, 22 to 25 minutes. (You should have about 3 1/2 cups cooked pear slices.) Remove pears from oven, and cool completely, about 20 minutes.
Place an empty baking sheet on bottom rack of oven. Increase oven temperature to 400°F. (Do not remove pan while oven preheats.)
Place pear slices in a large bowl. Add brown sugar, cornstarch, salt, cinnamon, nutmeg, sage, pear nectar, and lemon juice. Toss gently to coat. Spoon pear mixture over goat cheese mixture in pie plate. Top pear mixture evenly with butter. Place parchment paper with dough lattice over pear mixture; gently remove parchment from under lattice. (Or invert lattice onto pear mixture and peel off parchment.) Lightly whisk together egg white and 1 tablespoon water. Brush egg wash around edge of pie, and press lattice into edges to secure. Brush egg wash over lattice; sprinkle with turbinado sugar. Chill pie 15 minutes. Place pie on hot baking sheet on bottom rack of oven, and reduce oven temperature to 350°F. Bake until edges of crust are golden brown, 48 to 50 minutes. Loosely cover pie with aluminum foil to prevent overbrowning, and continue to bake until pears are tender and crust is golden, 15 to 20 more minutes. Cool completely on a wire rack, 3 to 4 hours. Cut into 12 slices.