Preheat oven to 350 degrees Fahrenheit.
In a food processor, crush graham crackers until they resemble fine crumbs. Melt 6 Tbsp butter and add to crumbs. (If any crumbs are still dry, melt 1 more Tbsp of butter and add to crumbs.) Press evenly in the bottom of a standard 9-inch pie dish. Bake for 8-10 minutes or until golden brown.
In a medium bowl, just before crust is done, combine all filling ingredients with a whisk until well blended and thick. Pour into hot crust and bake an additional 10-12 minutes until filling is solid when jiggled in the pan.
Cool completely and then refrigerate for 3 hours, or until chilled. Top with whipped cream before serving. (Whisk heavy whipping cream and powdered sugar in a stand mixer until stiff peaks form. Dollop or pipe onto top of pie.)
*This recipe can be used for key lime pie bars as well. Just press the crust into a square baking dish and half the recipe for the filling; follow the rest of the steps as usual.
*1 key lime = 2-3 tsp of juice.