Get your pie crust ready. Prebake per recipe instructions. Let it cool while you make the syrup and filling.
Lime syrup
Zest and juice the limes. Set aside for the filling.
Toss the rinds into a non-reactive bowl and cover with a cup of sugar.
Mix with a spoon every so often until the sugar is completely dissolved and you are left with sweet limey goodness.
Strain the syrup through a fine mesh sieve, pressing the rinds with a ricer or cheesecloth to get out all the essential oils. Discard the rinds.
Refrigerate in a glass canning jar or bottle. Will keep for up to 3 months.
Filling
Mix together the sugar, cornstarch, and salt in a heavy 3-qt sauce pan. Add in eggs, lime juice, lime zest, and milk, whisking until smooth. Heat over medium-low flame for about 5 minutes, gently whisking until hot.
Turn heat up to medium, continuing to whisk for about 3 more minutes as it thickens. When mixture comes to a boil, bubbles starting to appear at the edges, set a timer for 2 minutes and whisk until the timer goes off.
Remove from heat. Pour mixture through a fine mesh sieve, helping it through with a spatula when necessary to get every last drop into your prepared pie crust. Let cool completely.
Lime-Kissed Whipped Cream
Pour the cream and lime syrup into a bowl and whisk by hand, handmixer, or stand mixer until fluffy.
(Alternatively, you can simply lightly sweeten the whipped cream with powdered sugar and whip.)
Finishing Touches
Once pie has cooled, cover and refrigerate it for a couple of hours or overnight. Cover with whipped cream, then use a wet knife to cut. Leftovers will keep for up to 1 week in the refrigerator.