Step 1

Preheat the oven to 300 degrees Fahrenheit and then line a square baking pan (8X8Xwith foil.

Step 2

Combine graham cracker crumbs with brown sugar and butter in a small bowl. Stir until a sandy mixture forms.

Step 3

Press the mixture into the bottom of the prepared baking pan.

Step 4

Bake for about 12 to 15 minutes or until the crust is golden brown. Set aside and let cool completely.

Step 5

Whisk together sweetened condensed milk, lime juice, egg yolks, and 1 tbsp. lime zest in a medium bowl. Combine well.

Step 6

Carefully and evenly pour on the cooled crust.

Step 7

Bake filling at 300 degrees Fahrenheit for about 30 to 40 minutes.

Step 8

Put the pan on a cooling rack and let cool for about 2 hours.

Step 9

To make the topping, beat heavy cream, sugar, and vanilla in a medium bowl with an electric hand mixer on medium-high speed. Beat until stiff peaks form.

Step 10

Spread topping evenly over cooled bars. Garnish with lime zest if desired.

Step 11

Leave in the fridge for at least 2 hours before slicing and serving.