In a food processor, add in the gingersnap cookies, sugar, ground ginger and salt. Pulse until fine crumbs are formed.
Add in the melted and cooled butter and pulse 8 to 10 times until the crumbs are coated with butter.
Firmly press the crumbs into a 9 inch pie pan. The book recommends a metal pan, but I only had glass.
Place into the oven and bake for 12 minutes or until golden brown. Let the crust cool and work on the filling.
Tangerine filling
In a medium saucepan, add in the whole eggs, egg yolks, sugar, cornstarch, and salt. Whisk to combine.
Whisk the tangerine juice and lemon juice into the egg/sugar mixture until incorporated.
Place over medium heat and whisk constantly until the filling becomes thick and can coat the back of a wooden spoon. It took mine about 8 minutes to thicken completely.
Strain the curd with a fine mesh strainer to remove any lumps and cooked egg. Don't press a spatula against the strainer, instead try jiggling and tapping the strainer.
Whisk the tangerine zest, lemon zest, granted ginger, and cubes of butter into the curd. Whisk until the butter is completely melted and incorporated into the filling.
Pour the filling into the prepared crust.
Place into the oven and bake for 10 - 15 minutes until the pie is set and the center is slightly jiggly. It will resemble jello in the center. Mine took 13 minutes. Remove from the oven and let cool to room temperature.
Place the pie into the fridge for at least 4 hours to overnight. I let mine chill overnight before adding the topping.
Topping
In a cold mixing bowl, add in the heavy cream and granulated sugar. Whip using a hand mixer until soft peaks form.
Top the chilled pie with the topping. Sprinkle the tangerine zest and crystallized ginger for decoration. I didn't have the ginger, but I added a slice of lemon.