Preheat oven to 425 degrees F.
Prepare pie crust. Mix together flour with salt and cold butter with a pastry cutter. Blend until mixture resembles coarse sand. Add ice water, 1 tablespoon at a time until dough starts to come together. Shape dough into round disc, wrap with plastic wrap, and chill for at least 30 minutes and up to 24 hours.
Dust clean work counter with flour. Roll out pie crust to a 12-inch circle. Drape dough onto pie pan, pressing dough into pan. Crimp edges to create a crust. Prick bottom of the crust with a fork several times to prevent it from rising up when baking. Place parchment paper on top and fill with either pie weights or beans. Bake crust for 10 minutes.
Remove parchment paper and weights from pie crust. Brush crust with egg wash and bake 12-15 minutes or until golden brown. Remove from oven and let cool completely.
Meanwhile, prepare earl grey white chocolate mousse. Combine 2 cups heavy cream with 2 tablespoons earl grey loose tea leaves and bring to a simmer in a medium saucepot over medium-low heat. Do not bring to a boil. Reduce heat to low and continue to simmer for 5 minutes. Turn off the heat and let cream sit for 1 hour. Strain infused cream, discarding tea leaves.
Beat together egg yolks with 2 tablespoons sugar in a medium bowl. Add 1 cup infused cream and 2 tablespoons cornstarch. Bring a pot of water to a simmer (not boiling) and place the bowl on top, making sure the bowl is not directly touching the water. Continue to stir until the mixture becomes thickened, about 10-12 minutes. Remove from heat.
Melt white chocolate in the microwave at 20-second intervals until it begins to melt. Add white chocolate to egg and cream mixture, stirring to combine. Let cool completely and chill in the fridge for 1 hour or until thickened. The cream should set into a solid mass.
With the remaining infused cream, add additional heavy cream to amount to 1 cup total. Chill until cold.
Combine 3 ½ ounces bittersweet chocolate with ¼ cup plus 2 tablespoons heavy cream in a medium bowl. Microwave for 15 seconds and stir to combine. Continue to microwave at 15-second intervals until chocolate begins to melt. Stir until well combined. Spread ganache on bottom of pie crust in an even layer. Chill for 30 minutes or until set.
Whip remaining infused cream until stiff peaks form. Add half of the whipped infused cream into egg-cream mixture, beating until well combined. Fold in remaining whipped infused cream until combined. Pour into pie crust and smooth the top. Let chill overnight.
Prepare whipped cream. Whip ½ cup heavy cream with 2 tablespoons powdered sugar until stiff peaks form. Place large dollops of whipped cream on the pie and garnish with chopped pistachios. Serve.