Instructions

For the crust:  

Step 1

Preheat oven to 350° F.  

Step 2

In a small saucepan, melt butter over medium heat. Cook, swirling occasionally, until butter begins to foam and turn light amber in color and the milk solids begin to brown. The butter should smell nutty and fragrant. Remove from heat and immediately transfer to a small bowl to prevent burning. Cool to room temperature.  

Step 3

Meanwhile, place potato chips in the bowl of a food processor. Pulse for about 30 seconds until finely ground. Add flour, and pulse once or twice more to combine.  

Step 4

With the food processor on, slowly stream in browned butter and mix until the crumb begins to hold together.  

Step 5

Pour crust into tart pan and firmly press it along the bottom and up the sides of the pan. (It may be a little crumbly, but should hold together when pressed.) 

Step 6

Bake for 15 minutes, rotating halfway through, until the edges are golden brown. Remove from oven and cool completely.  

For The Filling:  

Step 1

In a large bowl, combine egg yolks, sweetened condensed milk, key lime/lime just, zest, and salt. Whisk until smooth and homogenous. (If you have time, transfer the filling to a airtight container and refrigerate overnight. This allows the air bubbles to settle and makes for a smoother pie.) 

Step 2

When you are ready to bake. Preheat the oven to 300° F and pour filling into your prepared crust. Set tart pan on a baking sheet inside the oven and bake for 40-45 minutes until filling is set, and has a slight jiggle when gently shaken. Remove from oven and let cool completely before transferring to the refrigerator to chill.  

Step 3

Top with whipped cream or toasted Swiss meringue and enjoy! 

How to make Swiss Meringue:  

You can use the leftover egg whites to make an easy peasy Swiss meringue for topping your pie. All you need is egg whites and sugar. Culinary school says that Swiss meringue ratios are usually one part egg whites to two parts sugar, but I sometimes go for a 1:1.5 ratio. I usually start with about 60 grams egg whites (from about 2 eggs) and about 100 grams granulated sugar. Combine whites and sugar in a heat-proof bowl and set over a double-boiler. Cook, whisking frequently until the mixture is hot to the touch and sugar has completely dissolved. Transfer to the bowl of a stand mixer and whip on medium-high speed until cooled, thick, and glossy. Pipe or swirl it on top of your pie and use a blow torch (carefully) to get those pretty toasted edges.  

Notes:  

I wanted a sweet and salty combination so I went for a potato chip crust. If you are feeling a little more traditional, you can always substitute the potato chip crust for a graham cracker crust (either homemade or store-bought). Because graham crackers contain gluten and potato chips do not, simply substituting graham crackers for the potato chips in this recipe will not work. You can google a graham cracker crust recipe or fly by the seat of your pants and combine graham cracker crumbs with a little sugar and enough melted butter to make it hold together.