Crust

1. Preheat the oven to 350°F. Grease an 8x8-inch baking dish with butter. Cut a piece of parchment paper to fit the width of the pan and long enough to hang over the sides. Press the parchment into the pan, creating a parchment sling.

2. In a large mixing bowl, whisk the graham cracker crumbs, sugar, cinnamon, and salt together.

3. Add the melted butter and use a rubber spatula to stir until all the crumbs are coated. The mixture should look like wet sand.

4. Pour the crumbs into the prepared baking dish and use your fingers to spread them into an even layer.

5. Using a small measuring cup or flat-bottomed drinking glass, press the crust tightly into the bottom of the pan.

6. Bake the crust for 10 minutes, until it has just started to darken around the edges. Then let cool completely on a wire cooling rack.

Filling

1. Reduce the oven temperature to 325°F.

2. Zest the limes, then set 4 teaspoons aside for the filling and 1 teaspoon aside for the garnish.

3. Juice the limes to get 1 cup of lime juice.

4. In a large mixing bowl, whisk the egg yolks, condensed milk, key lime zest, key lime juice, and salt together until fully incorporated into a smooth yellow custard.

5. Pour the filling over the cooled crust and bake for 18 to 20 minutes, until just set. You can test for doneness by gently shaking the pan—the filling should jiggle slightly.

6. Return the pan to the cooling rack and let cool to room temperature.

7. Once cool, cover the pan with plastic wrap and chill in the fridge for at least 2 hours or up to overnight.

Whipped Topping

1. Pour the heavy cream into a large, chilled mixing bowl.

2. Use a whisk or electric mixer fitted with the whisk attachment (if using an electric mixer, start on a low speed and gradually increase to medium) to whip the cream.

3. Once the cream starts to thicken, add the powdered sugar and salt.

4. Continue whipping the cream until it forms medium-stiff peaks (the cream stands on its own when you remove the whisk).

Finishing the Bars

1. Remove the chilled bars from the fridge and, using the parchment sling, lift the bars out of the pan and place on a cutting board.

2. Cut the bars straight down with a warmed and dried chef’s knife. Repeat warming and drying the blade as needed to cut the bars.

3. Cut the bars into 8 pieces.

4. Top each bar with an even layer of whipped cream dolloped using a small spoon and a sprinkle of lime zest.