How to Make It
Preheat oven to 350°F with rack in lowest position. Roll out pie crust on a lightly floured work surface to about 14 inches in diameter; place in a 9-inch pie plate. Using your fingers, tuck overhang under so crust just covers the lip of the plate. Crimp edge and freeze for 15 minutes.
Toss cranberries, strawberries, sugar, cornstarch, and salt in a large bowl. Transfer to frozen pie shell and return to freezer.
Meanwhile, make the crumb topping: Combine flour, sugar, cinnamon, ginger, and salt in a medium bowl. Add butter and use your fingers to work it into dry ingredients until clumps form. Remove pie from freezer, scatter crumb topping over fruit, and place pie on a rimmed baking sheet. Bake until crust and topping are golden brown and fruit is bubbling, 75 to 85 minutes. Let cool for at least 4 hours before slicing.