For an impressive presentation, use coconut halves instead of ramekins for this recipe. To prep the coconuts, first drain the milk by using a corkscrew. Once drained, bake the coconuts in a 400 degree F oven for 10 to 15 minutes. Use a hammer to crack open coconuts to create halves. Create 4 foil rings and place them under the coconut shells for support.
Preheat oven to 375 degrees F.
Rub the inside of the ramekins or coconut shells with softened butter. Sprinkle granulated sugar into the molds, and twist so the sugar crystals coat the inside of the ramekins or coconut shells. Shake out any excess sugar.
In a saucepan, combine the melted butter, 1/3 cup sugar, the flour and cornstarch. Slowly whisk the warm milk into the mixture. Bring to a boil, and reduce to low heat, stirring constantly, simmer until thick enough to coat the back of a wooden spoon. Slowly whisk the thickened mixture into the egg yolks a little at a time to temper them. Cover and allow to cool to room temperature. Stir in lime zest and juice.
In a large bowl, beat the 6 egg whites, remaining 2 tablespoons sugar and a pinch of salt at high speed with an electric mixer until soft peaks form. Gently fold the whipped whites into the cooled egg mixture.
Divide the souffle batter among the ramekins or coconut shells. If using the coconut shells, use your finger to clear the inside of the coconut rims, giving space for the souffle to rise. Bake until puffed and lightly browned, about 35 to 40 minutes.
Top with toasted coconut, sprinkle with confectioners' sugar and garnish each a slice of lime. Serve immediately.