1To make the tart, add the flour, cocoa powder and salt to a mixing bowl and stir to combine.
2Cream the butter and sugar in a stand mixer, fitted with the paddle attachment, until light and fluffy, about 3 minutes.
3Add the egg and mix until fully incorporated.
4Add the dry ingredients and mix until combined.
5Shape the dough into a disk, wrap it in plastic wrap and refrigerate for an hour.
6Preheat the oven to 350 degrees. Roll the dough between two sheets of parchment, sprinkled with flour, to form a circle that is a 1/4” thick. Remove one side of the parchment and carefully invert the dough into a tart pan lightly sprayed with non-stick spray.
7Remove the top sheet of parchment and, with your fingers, press the dough into all corners of the tart pan. Use a paring knife to trim any excess dough from the top of the tart pan. Use scraps to repair any tears in the dough – it is very forgiving. With a fork, punch holes into the bottom portion of the dough and then refrigerate for twenty minutes. Line the tart shell with a piece of parchment and fill the cavity with pie weights or dry beans.
8 Bake for 15 minutes, remove the parchment and weights and bake for an additional 15 minutes, until the tart shell has barely any give when pressed. Allow the shell to cool completely.
9Remove the shell from the tart pan and carefully wrap it in plastic wrap until use. The tart shell can be made up to three days in advance.
10To make the coffee cream, combine the milk, coffee, salt, vanilla and half of the sugar in a shallow sauce pan, bring to a simmer. Meanwhile, in a small bowl, combine the remaining sugar, flour and cornstarch. Add it to the egg yolks and whisk until fully incorporated and the eggs begin to lighten in color. When the milk mixture begins to simmer, temper the eggs by slowly ladling the hot milk mixture into the eggs, being sure to whisk the whole time.
11Repeat with an additional two ladlefuls of hot milk. Add the tempered eggs into the milk saucepan and bring to a boil.
12 While whisking continuously, allow the mixture to boil for two minutes. Transfer the coffee cream to a bowl and cover the top with plastic wrap so that it does not develop a skin. Refrigerate until cool, at least two hours. The coffee cream can be made up to one week in advance.
13To assemble the tart, vigorously stir the coffee cream to remove any lumps. In a large bowl, whip the heavy cream to medium peaks.
14Add the coffee cream and whisk to combine.
15Transfer the coffee cream into the prepared tart shell.
16Top generously with the shaved chocolate.
17Refrigerate until serving, up to two hours.