How to Make It
Preheat the oven to 350°. In a food processor, finely grind the Oreos. Pulse in the butter. Lightly spray four 4 1/2-inch fluted tartlet pans with removable bottoms; press the ground Oreos into the bottoms. Set the pans on a baking sheet and bake for 8 minutes, or until the edges look dry. Let cool.
In a bowl, whisk the yolks, condensed milk, 1/3 cup of the Key lime juice and the lime zest. Pour the filling into the pans and bake at 325° for about 15 minutes, until the edges are just firm. Let cool for 30 minutes, then freeze until very cold, about 2 hours.
In a small saucepan, combine the 3 tablespoons of sugar with 3 tablespoons of water, the lime leaves and the salt. Cook until the sugar has dissolved, then let cool. Discard the lime leaves. Stir in the remaining 1/3 cup of lime juice and refrigerate.
Sprinkle 2 teaspoons of the sugar over each tart and caramelize with a blow torch. Unmold the tarts and place in shallow bowls. Pour in the Key lime sauce and serve.