For the crust: using a food processor, blend graham crackers with butter and brown sugar then press crumbs into a glass pie pan. Bake for 5 minutes or microwave for 1 minute then let cool while you prepare the key lime filling.
For the filling: beat together key lime juice, sour cream, sweetened condensed milk, lime zest and salt.
Pour into crust, smooth out the top, and chill ideally for 2 hours or more.
Top with whipped cream poufs along the outside edge of the pie or if you're taking the pie somewhere, leave the whipped cream on the side. Garnish with 1 circular lime slice in the center of the pie. You could also spread whipped cream or Cool Whip across to whole top of the pie. Up to you!