Thaw your pie crust for 10 minutes on the counter. Whisk together the egg and tsp. of water. Using a pastry brush spread the egg wash over the pie crust. Prick the pie crust with a fork generously, even on the edges. Bake according to package directions. Mine took 12 minutes.
Lemon Layer:
Zest the lemons. Cut the lemons in half and juice them, discard seeds.
Whisk the egg yolks in a small bowl, set aside. Have your butter out and ready as well.
In a medium sized sauce pan add the water, sugar, salt, lemon zest, lemon juice, flour and cornstarch, whisk together. Set the heat to medium high heat. Bring this mixture to a boil, whisking constantly.
Add the butter to the lemon mixture, stir and let melt in. Add a scoop of this hot mixture to the egg yolks bowl, stir them together. Add this egg yolk mixture to the rest of the lemon filling. Stir. Let boil for 1 more minute, whisking constantly.
Pour the lemon filling in to the prepared and baked pie crust. Refrigerate for an hour or longer.
Sour Cream Layer:
Preheat oven to 350 degrees.
In a small bowl mix together the sour cream and sugar. Spread this mixture over the lemon layer.
Bake for 7 minutes.
Remove from oven and refrigerate for at least 3 hours before making and topping with whipped cream in next step.
Whipped Cream
In a large bowl add the heavy cream and sugar. Using a hand mixer or stand mixer with whisk attachment, blend until stiff peaks form.
I used a 16 inch piping bag and a wilton 1M piping tip to decorate the pie with the whipped cream. Keep refrigerated until ready to serve.