• Preheat oven to 350 degrees Fahrenheit (177 degrees Celsius).
  
• Line a 9” square baking dish (preferably ceramic or glass) with parchment paper (with handles) then lightly grease.
  

Make the Key Lime Filling

• In a large bowl whisk the condensed milk, sour cream, egg yolks, key lime juice, and vanilla together until smooth. If desired, whisk in lime zest. Set aside.

Make the Graham Cracker Crust

• If necessary – make the graham cracker crumbs by breaking up 12 full graham crackers into a high powered blender or food processor fitted with the “S” blade. Blend or process until they reach the consistency of fine crumbs with no chunks left.
• In a large bowl, mix together the graham cracker crumbs, sugar and cinnamon.
• Add the melted butter and stir until combined.
• Press the crust mixture evenly into the bottom of the prepared baking dish.
• Bake in preheated oven for 5 minutes, then remove the crust from the oven.

Assemble & Bake

• Pour the key lime filling into the partially baked crust.
• Return to the oven and bake for 22-27 minutes or until the edges of the filling look set and it’s just very slightly jiggly.
• Remove from the oven and set the pie on a wire rack to cool. Transfer the bars on the rack to the refrigerator and chill for at least 6 hours (or preferably overnight)
• Once chilled, use a knife to release the bars from the edge of the baking dish. Then, lift them out of the dish and put them on a cutting board.
• Cut into 16 slices, then decorate the bars with homemade whipped cream.
• Transfer to a serving plate and put in the refrigerator until you're ready to serve. Serve them cold.