Prepare the crust
Preheat the oven to 350 degrees.
In a medium bowl, mix together graham crumbs, brown sugar, and melted butter. Mix until combined.
Press this mixture evenly into the bottom of a 9 inch pie pan.
Bake the graham crumb crust at 350F for 10 minutes.
Remove from the oven.
Prepare the filling
While the crust is baking, prepare the filling.
Using an electric hand mixer, combine the key lime juice, zest, sweetened condensed milk, sour cream, 2 egg yolks, and powdered sugar until combined.
Pour the filling into the baked crust.
Bake the Key Lime Pie
Bake the pie at 350 degrees for 15 minutes. The pie should be just slightly jiggly in the center when done. If the pie is very jiggly, leave it in and check it every 5 minutes.
Remove the pie from the oven and allow it to cool to room temperature.
Then refrigerate the pie for at least another 2.5 -3 hours.
Serve with whipped cream and lime zest or lime slices if desired.