To Make Crust: Preheat oven to 350 degrees. Spray a 23 cm pie plate with nonstick cooking spray. In a medium sized bowl, beat egg white lightly with a fork until frothy. Add graham cracker crumbs, butter and oil and blend with your fingertips until thoroughly combined. Press the mixture in an even layer on the bottom and sides of the pie plate. Bake for 10 minutes, or until lightly browned. (Do not be concerned if there are small cracks.) Cool on a rack.

To Make Filling: In a medium-sized metal bowl, whisk together milk, yogurt, lime juice and zest. In a small saucepan, sprinkle gelatin over 2 tbs. cold water. Let soften for 1 minute. Heat over low heat, stirring, until the gelatin is dissolved. Whisk into the lime mixture. Set the bowl over a larger bowl of ice water, stirring occasionally, until it begins to thicken, 15 20 minutes. Turn into the pie shell and chill in the refrigerator while you prepare the meringue.

To Make meringue: Preheat the broiler. In a small saucepan, combine sugar with half cup water. Bring to a boil, stirring occasionally. Cook over medium-high heat, without stirring, until syrup registers 120ºC and is at the soft-ball stage (when a bit of syrup dropped into ice water forms a pliable ball) about 5 minutes. Remove syrup from heat. Set aside. In a large mixing bowl, beat egg whites with an electric mixer on medium speed until frothy. Add cream of tartar and beat on hight speed just until soft peaks form. Return the syrup to the heat until it boils. Gradually pour hot syruup into egg whites but not directly onto the beaters, beating constantly. Continue beating until egg whites are cool and very stiff, about 5 minutes. Blend in vanilla. Remove the pie from the refrigerator and spread the meringue over the top, sealing to the edge of the crust and swirling roughly on top. Place the pie under the broiler for 1-2 minutes, or until lightly browned. Let cool to room temperature, the refrigerate until the filling has set, for 5-8 hours. Garnish with fresh lime slices just before serving.