- Step 1
Position the rack in the centre of the oven and preheat the oven to 180C (160C fan). Lightly spray a 35cm x 11cm rectangular tart pan with the cooking spray.
- Step 2
To make the crust, in a medium bowl, whisk the flour, cocoa powder, and salt to blend. Using an electric mixer fitted with the paddle attachment, beat the butter and sugar in the mixer bowl until pale and fluffy. Reduce the speed to low speed and gradually stir in the flour mixture.
- Step 3
Press the mixture into the prepared tart pan to cover the bottom and sides evenly. Using a fork, prick the bottom of the dough all over. Bake for about 20 minutes, or until the pastry is cooked and looks dry and set. Transfer the pan to a rack and cool completely.
- Step 4
To make the caramel, in a medium heavy saucepan, stir the sugar and water over medium heat for about 5 minutes, or until the sugar dissolves. Using a moistened pastry brush, brush down the sides of the pan to remove any grains of sugar. Boil without stirring for about 5 minutes, or until the syrup turns a deep golden brown color and registers 200°C on a candy thermometer. Add the golden syrup and then the cream and cook for about 30 seconds, or until the cream is slightly reduced. Remove the saucepan from the heat and whisk in the butter. Strain through a fine sieve. Cool the caramel slightly and mix in the pink salt.
- Step 5
Pour the caramel into the cooled tart shell. Refrigerate for about 2 hours, or until set.
- Step 6
To make the ganache, in a small heavy saucepan, heat the cream over medium-high heat just until hot. Remove the pan from the heat, add the chocolate, and set aside for 1 minute. Whisk the mixture just until blended. Pour the ganache into the tart shell to evenly cover the caramel layer. Refrigerate for about 2 hours, or until set.
- Step 7
Remove the tart from the tart pan and garnish with the hazelnuts. Slice and serve.
The crust dough can be made up to 2 days ahead, wrapped in plastic and refrigerated. The tart can be completed up to 1 day ahead, covered and refrigerated. Bring to room temperature before serving.