For the crust-
Preheat the oven to 350°C.
Combine in a food processor, the confectioners' sugar, flour, butter, water and process until the mixture forms a ball.
Using your fingers, press the dough into a 12-inch tart pan with a removable bottom. Pat until the crust is even.
Bake for 15 to 23 minutes, until very lightly browned. Set aside to cool.
For the filling:
Firstly, mix powdered sugar, cocoa powder, vanilla extract and milk.
Stir well till the mixture forms smooth and creamy.
Pour into the tart shell and refrigerate for 2 to 4 hours to set or overnight.
Lightly sprinkle salt flakes, if desired. Serve.
