01 - In a large mixing bowl, combine sweetened condensed milk, Greek yogurt, key lime juice, lime zest, vanilla extract, and salt. Whisk until thoroughly blended and smooth.
02 - Using an electric mixer or whisk in a chilled bowl, beat the heavy cream to stiff peaks. Gently fold the whipped cream into the lime mixture, maintaining as much volume as possible.
03 - Line a 9x9-inch pan with parchment paper. Pour the ice cream mixture into the pan, level the surface, and freeze for at least 4 hours or until completely firm.
04 - Set the oven to 350°F (175°C) and line a baking sheet with parchment paper.
05 - In a separate bowl, stir together graham cracker crumbs, all-purpose flour, baking powder, and salt.
06 - Beat softened butter with brown sugar until light and fluffy. Add egg and vanilla extract, mixing until incorporated.
07 - Gradually blend the dry ingredients into the butter mixture, mixing only until just combined to avoid overworking the dough.
08 - Portion 16 tablespoon-sized balls of dough onto prepared baking sheet and flatten gently. Bake for 8–10 minutes until golden at the edges. Allow cookies to cool completely on a wire rack.
09 - Once ice cream is firm, use a round cookie cutter matching the cookies’ diameter to cut out ice cream rounds.
10 - Sandwich each ice cream round between two cookies. Serve at once or wrap each in parchment and freeze until needed.