Back
Key Lime Slab Pie
5 from 12 votes

Key Lime Slab Pie

The Key Lime Slab Pie uses a graham cracker crust baked in a large rectangular pan, filled with a tangy key lime custard made from lime juice, zest, and egg yolks thickened with cornstarch. Topped with whipped cream flavored with powdered sugar and lime juice, this pie offers a creamy, citrus-forward dessert with a firm crust base and rich lime flavor.

Course: Dessert, Snacks, Others
Cuisine: American

Ingredients

Crust:
  • 3 ½ cups graham cracker crumbs (about 25 whole graham crackers)
  • 3/4 cup butter plus 2 Tablespoons melted
  • 1/2 cup granulated sugar
Filling:
  • 1 cup granulated sugar
  • 6 tablespoons cornstarch
  • 1/4 teaspoon kosher salt
  • 2 cups milk whole
  • 4 large egg yolk
  • 1 tablespoon lime zest
  • 1/2 cup lime juice fresh
  • 2 tablespoons butter
Topping:
  • 2 cups heavy whipping cream
  • 3/4 cup powdered sugar
  • 1/4 cup lime juice fresh

Instructions

    Cup of Yum
  1. Preheat over to 350 degrees F. Spray a 15x10-inch jelly roll pan with cooking spray. Set aside.
  2. For Crust: In a large bowl mix together the graham cracker crumbs, melted butter and sugar. Pour crumb mixture into prepared pan and evenly spread. Use the bottom of a measuring cup to press the mixture firmly down and up the sides of the pan. Bake 10 minutes. Let cool on a wire rack.
  3. Filling: In a large saucepan whisk together the sugar, cornstarch and salt. Whisk in the milk and bring to a boil over medium heat, stirring constantly, continue cooking 2 minutes. Remove from heat. Put the egg yolks into a medium bowl and slowly whisk some of the hot milk mixture into the egg yolks (I whisk in about 1 cup). Pour the egg yolk mixture back into the pan with the remaining milk mixture. Cook, whisking constantly, until thick and bubbly, about 3 to 4 minutes. Remove from heat and stir in lime zest, lime juice and butter. Pour into a large bowl and place a piece of saran wrap right up against the top of the mixture. Put in refrigerator and cool completely.
  4. Once mixture is cool, pour into prepared crust and spread evenly.
  5. Topping: In a large bowl, beat whipping cream, powdered sugar and lime juice on high until still peaks form. Spread topping over lime filling and refrigerate at least 4 hours. Cut into desired size bars and serve. Store in refrigerator.
  6. *Notes: The original recipe calls for bottled key lime juice, but I always just use fresh lime juice (not key limes, they’re so small and take way too many to get enough juice out of). Feel free to use the bottled key lime juice or just use regular limes.
  7. Also, I don’t usually buy whole milk, but I always half & half in my fridge so to save me a trip to the store, I use 1 cup half & half and 1 cup milk (1%) for the filling.