Thanks to an exceptionally high butterfat content and extra smoothness from sweetened condensed milk, the lime ice cream used for this pie's filling doesn't need an ice cream maker—just pour it into your prepared pie crust, freeze for a few hours, and slice.
- For graham cracker crust:
- 10 graham crackers
- 1/2 teaspoon kosher salt
- 3 tablespoons sugar
- 5 tablespoons unsalted butter, melted and slightly cooled
- For lime ice cream:
- 1/2 cup lime juice
- 1 tablespoon freshly grated lime zest from 1 to 2 limes, plus more for garnish
- 3/4 cup sweetened condensed milk
- 1 cup cream
- 1/4 teaspoon kosher salt
For pie crust: Heat oven to 375 °F with an oven rack in the middle position. In a food processor, pulse graham crackers with sugar and salt until they form a fine powder. Pour in butter and pulse until crumbs become a coarse meal, scraping down sides of the bowl as needed.
Transfer crumbs to pie plate or tart pan and press into sides and against bottom for an even thickness all over. Refrigerate for 15 minutes, then bake until crust darkens in color and smells slightly nutty, about 15 minutes. Remove from oven and cool completely, then store in freezer until ready to fill with ice cream.
For the ice cream: In a medium mixing bowl, whisk together lime juice, zest, condensed milk, and cream. Stir until mixture thickens, about 1 minute, and add salt to taste.
To assemble: Pour ice cream base into to pie crust, spreading it evenly across with a rubber spatula, then chill in freezer until firm, 2 to 3 hours. Let pie sit out on counter for 5 minutes before serving, then garnish with lime zest and serve.