Step 1: Prepare the Crust
1. Mix Crust Ingredients: In a medium bowl, combine the graham cracker crumbs, granulated sugar, and melted butter. Mix until the crumbs are evenly coated and resemble wet sand.
2. Form Crusts: Press the mixture firmly into the bottom of mini pie pans or muffin tins to form an even layer. You can use the back of a spoon or your fingers to pack it down.

Step 2: Make the Filling
1. Combine Filling Ingredients: In a large bowl, whisk together the sweetened condensed milk, key lime juice, and lime zest until smooth.
2. Whip Cream: In a separate bowl, whip the heavy cream and powdered sugar together until stiff peaks form.
3. Fold Together: Gently fold the whipped cream into the key lime mixture until well combined and smooth.

Step 3: Assemble the Pies
1. Fill Crusts: Spoon the key lime filling into the prepared crusts, smoothing the tops with a spatula.
2. Chill: Cover the mini pies with plastic wrap and refrigerate for at least 2 hours, or until set.

Step 4: Serve
1. Garnish: Once chilled, remove the pies from the refrigerator. Garnish with lime slices, lime zest, and whipped cream if desired.
2. Enjoy: Serve chilled and enjoy your delicious No-Bake Mini Key Lime Pies!