2 teaspoonsfinely grated lime zest, plus more for garnish
5 tablespoonsjust-squeezed lime juice
1 pinchkosher salt
Instructions
Make the streusel. Break up the graham crackers with your hands and add to a food processor. Pulse until flour-like. Add the sugar and salt and pulse to combine. Evenly distribute the butter on top. Pulse until a cookie-like dough forms. Dump onto a plate and use your fingers to create lots of clumps. Freeze until completely firm.
Meanwhile, preheat the oven to 325° F. Line a rimmed sheet pan with a silicone mat or parchment. When the streusel is mostly frozen, add it to the prepared sheet pan and bake for 15 to 20 minutes until firm, rotating halfway through. Cool completely before making the posset.
Make the posset. Combine the heavy cream, sugar, and lime zest in a large pot. Like, much larger than you think you need—the cream loves to boil over. Set over high heat and bring to a boil. Adjust the heat to keep boiling for another 5 minutes. Turn off the heat and whisk in the lime juice and salt. Let cool for about 15 or so minutes.
Add a layer of graham cracker streusel to the bottom of 4 ramekins or glasses or other single-serving dishes. Slowly pour the posset on top, evenly dividing between the dishes. Chill until cold and set.
Garnish with lime zest and serve with the rest of the streusel to sprinkle on top.