To make crust, mix sugar and butter until creamy. Add whole egg and mix.
Sift cocoa powder, baking powder, baking soda, salt and flour. Add to mix. When all is combined, place between parchment paper. Flatten slightly and chill 1 hour.
Heat oven to 350° F.
Roll dough to 1/8-inch thickness and place in pie pan or tart pan. Cut circle of parchment large enough to cover bottom and sides of dough. Place paper on dough. Place rice on paper. Bake 10 minutes. Remove parchment and rice. Bake for an additional 10 minutes. Let cool.
For filling, combine milk and egg yolks on slow speed. Slowly add Key lime juice while mixing on low until blended. Pour into crust. Bake at 350° F for 20 minutes. Chill until cold, preferably overnight. Garnish with sweetened whipped cream.Makes 10 Source: