01 - In a large bowl, whisk together the sweetened condensed milk, Greek yogurt, key lime juice, key lime zest, vanilla extract, and a pinch of salt until fully blended.
02 - In a separate chilled bowl, whip the heavy cream using an electric mixer or whisk until stiff peaks form. Gently fold the whipped cream into the lime mixture, ensuring a smooth and homogeneous blend.
03 - Line a 9x9-inch pan with parchment paper. Transfer and level the lime ice cream base into the pan. Freeze for a minimum of 4 hours, or until solid.
04 - Preheat the oven to 350°F (175°C) and line a baking sheet with parchment paper.
05 - In a bowl, mix together graham cracker crumbs, all-purpose flour, baking powder, and salt until evenly distributed.
06 - In a separate bowl, beat unsalted butter with brown sugar until pale and fluffy. Blend in the egg and vanilla extract until thoroughly incorporated.
07 - Gradually add the dry mixture to the butter mixture, stirring just to combine and avoid overmixing.
08 - Scoop 16 tablespoon-sized portions of dough onto the prepared baking sheet and flatten slightly. Bake for 8 to 10 minutes, until golden at the edges. Allow to cool completely on a wire rack.
09 - Remove ice cream from the freezer. Using a cookie cutter matching the size of the graham cookies, cut out 8 discs of ice cream.
10 - Place each ice cream disc between two graham cookies, pressing gently to adhere. Serve immediately, or wrap individually and store in the freezer until ready to enjoy.