In a large mixing bowl, combine the sweetened condensed milk and egg yolks. Mix until fully combined.
Add the lime juice, and once again mix until fully combined.
Pour the filling into your prepared graham cracker crust.
Bake for 25 to 30 minutes, or until very tiny cracks begin to appear around the edges of the pie.
Chill the pie for at least 3 hours in the refrigerator so the filling can fully set before serving.
Finish with Whipped Cream
In a stand mixer fitted with the whisk attachment, combine the cold heavy cream, sifted powdered sugar, and vanilla extract. Whip on medium-high speed until stiff peaks form and the cream holds its shape.
Spread the whipped cream evenly over the chilled key lime pie using an offset spatula or the back of a spoon. For a more decorative look, transfer it to a piping bag and pipe rosettes or swirls across the top.