Step 1

Preheat oven to 375F.

Step 2

Mix graham cracker crumbs, sugar, and butter in a small bowl. Press the crumb mixture into an 8" - 9.5" pie pan. Bake for 7 minutes. Cool for at least 30 minutes.

Step 3

Preheat oven to 350F

Step 4

Whisk together sweetened condensed milk, sour cream, lime juice, and lime zest in a medium bowl. Pour into prepared graham cracker crust and bake for 10 minutes.

Step 5

Let pie cool slightly before chilling. Chill for at least 3 hours.

Step 6

Beat heavy cream and sugar together in a mixer until stiff peaks form. Beat in vanilla. Spread or pipe the whipped cream on top of the cooled pie. Top with additional lime zest if desired.