Preheat your oven to 350 degrees Fahrenheit.

Add sweetened condensed milk, egg yolks, and sour cream to a large mixing bowl. With a hand mixer or stand mixer, beat them together until they are smooth and creamy. Lightly stir in lime juice and zest until combined.

Pour lime pie filling into graham cracker crust and bake for 15 minutes.

Carefully remove from oven and let cool on a cooling wire rack for at least half an hour at room temperature. Transfer to refrigerator and let chill for at least 2 hours or overnight.

Add heavy cream and sugar to a large mixing bowl. Whip cream until stiff peaks form with a hand mixer or stand mixer (or by hand).

When ready to serve, spread whipped cream on top of the pie and garnish with lime zest and slices.