How to Make It
Prepare the crust: Whisk together flour, milk 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 tablespoon ice-cold water; add up to 3 more tablespoons water, 1 teaspoon at a time, stirring just until dough begins to come together. Turn dough out on a lightly floured surface, and gently knead 1 or 2 times. Form dough into a disk. On a lightly floured surface, roll disk into a 12-inch circle. Fit dough circle into a 9-inch pie plate, fold dough edges under, and flute. Refrigerate piecrust at least 45 minutes or up to 1 day.
Prepare the filling: Place a baking sheet on bottom rack of oven, and preheat oven to 400°F. (Do not remove baking sheet while oven preheats.) Place butternut squash in a medium saucepan, and add water to cover squash. Cover and bring to a boil over medium-high. Reduce heat to medium, and cook, covered, until squash is very tender, 10 to 12 minutes. Drain and place squash in a large bowl. Using a potato masher, mash squash until smooth. Let squash cool to room temperature, about 30 minutes. Add brown sugar, cardamom, salt, cinnamon, nutmeg, allspice, sweetened condensed milk, and eggs to cooled butternut squash. Stir well to combine.
Melt butter in a small saucepan over medium. Cook until butter turns brown and has a nutty aroma. Remove saucepan from heat, and stir butter into squash mixture. Pour filling into chilled piecrust. Place pie in oven on preheated baking sheet. Reduce oven temperature to 350°F, and bake until filling is mostly set with a slightly jiggly center, 35 to 38 minutes. Let pie cool completely on a wire rack, 2 hours and 30 minutes to 3 hours.
Prepare the topping: Place crème fraîche in a medium bowl, and set aside. Place heavy cream in a large bowl, and beat with an electric mixer on medium-high speed until foamy. Gradually add powdered sugar to heavy cream, and beat until stiff peaks form. Very gently fold heavy cream mixture into crème fraîche. To serve, cut pie into 12 slices. Dollop slices with crème fraîche mixture; top with chopped candied pecans.