For the crust:
For the cupcakes:
Key lime curd
Preheat the oven to 350° F. Line two cupcake pans with paper liners. In a small mixing bowl, combine the graham cracker crumbs, sugar and melted butter; mix well with a fork. Drop about 1 tablespoon of the graham cracker mixture in the bottom of each cupcake liner and press down to line the bottom. (Note: the bottom of a squeeze bottle or shot glass works very well.) Bake for 5 minutes. Remove from the oven, and maintain the oven temperature.
To make the cupcakes, combine the cake flour, baking powder and salt in a medium bowl. Whisk together and set aside. Add the butter to the bowl of an electric mixer fitted with the paddle attachment. Beat on medium-high speed for 3 minutes, until light and creamy in color. Scrape down the sides of the bowl and beat for one more minute. Beat in the lime zest. Add the sugar to the butter mixture, ¼ cup at a time, beating 1 minute after each addition. Mix in the eggs one at a time until incorporated. Scrape down the sides of the bowl after each addition. Combine the buttermilk and the vanilla and coconut extracts in a liquid measuring cup. With the mixer on low speed, add the dry ingredients alternately with the wet ingredients, beginning and ending with the dry ingredients and mixing just until incorporated. Scrape down the sides of the bowl and mix for 15 seconds longer.
Divide the batter between the prepared paper liners, filling each about 2/3 of the way full. Bake 18-22 minutes, or until a toothpick inserted in the center comes out clean. Allow to cool in the pans 5-10 minutes, then transfer to a cooling rack to cool completely.
To assemble the cupcakes, use the cone method to make a well in the center of each cupcake. (I prefer the paring knife method for these cupcakes). Discard the cones. Fill each well with about 1½ tablespoons of the lime curd. To make the whipped cream, combine the heavy cream and confectioners’ sugar in the bowl of an electric mixer fitted with the whisk attachment. Whip on medium-high speed until stiff peaks form. Blend in the vanilla. Transfer the whipped cream to a pastry bag fitted with a decorative tip. Pipe a rim of whipped cream around the top of each cupcake, leaving the lime curd filling exposed. Garnish with key lime slices if desired.