Start by preheating your oven to 350°F. While it’s heating, grab graham cracker crust and set it on a baking sheet.

In a large bowl, whisk egg yolks until they’re just broken up. Now pour in both cans of sweetened condensed milk and whisk until everything’s smooth and well combined .

Here’s where the magic happens: slowly stream in key lime juice while whisking constantly. You’ll notice the mixture starting to thicken slightly – that’s the acid from the limes beginning to react with the condensed milk. Keep whisking until everything’s evenly mixed and looks silky smooth.

Pour the filling into graham cracker crust. Give the pan a gentle tap on the counter a few times to help any air bubbles rise to the surface. Pop it into your preheated oven and bake for 15-18 minutes. You’re looking for the filling to be just set – it should still have a slight jiggle in the middle when you gently shake the pan, but shouldn’t be liquid. If you see any browning starting to happen, that means it’s definitely done.

Let the pie cool on a wire rack for about an hour, then refrigerate for at least 3 hours or overnight.

When you’re ready to serve, make the whipped cream topping. Pour your cold heavy cream into a clean bowl, add the powdered sugar and vanilla, and beat with an electric mixer. Start on low speed to avoid splashing, then increase to medium-high. Watch carefully – you want soft peaks that gently curl over when you lift the beaters. If the peaks stand straight up, you’ve gone too far.

Spread or pipe the whipped cream over your chilled pie. If you’re using lime zest for garnish, sprinkle it on now – it adds a nice pop of color and extra lime flavor.