Instructions

Shortbread crust

Using a stand mixer fitted with the paddle attachment, cream the butter, powdered sugar, and salt until the mixture is light and fluffy. Add the egg and combine.

Add the flours and cocoa powder to the bowl and beat on low until the mixture is fully incorporated and the dough barely comes together. Use a rubber spatula to get the remaining flower incorporated, but do your best not to over mix.

Shape the dough into a disc. Wrap in plastic and refrigerate for 2 hours.

Preheat the oven to 400°F. On a lightly floured surface, roll out the dough to ¼-inch thickness. Using the bottom of a 9-inch tart pan with a removable bottom or a springform pan as a template, trim the dough to fit the pan bottom and to reach up the sides of the pan.

Grease the pan and carefully lay the dough inside the pan and press it into the bottom and sides, fitting evenly. Using a fork, poke dough to prevent it from puffing up. Freeze the dough for 15 minutes before baking. Place the tart pan on a rimmed sheet pan in the center of the oven. Bake for 15 to 20 minutes.

Hazelnut praline

Meanwhile, toast the nuts in a dry pan until they start to brown and have a nutty aroma. Add sugar and cook until it melts and is brown and caramelized. Pour onto a rimmed baking sheet lined with parchment paper. Leave to cool, and then once solid, roughly chop.

Tart filling

Over a pan of simmering water, melt the chocolate and butter together, then add in the hazelnut spread. Set aside to cool slightly. In another bowl over the simmering water, beat the egg, yolks, and remaining sugar until it's pale and fluffy. Remove from the heat and fold in the chocolate mixture.

When the shell is baked, remove it from oven and turn the heat down to 350°. Pour the chocolate mixture over the crust and spread evenly. Cook the tart for 20 to 25 minutes until the chocolate has almost set. Remove from the oven, scatter with the praline, and press the nuts into the filling a bit so they'll stay in place. Cool completely, then serve.