Preheat the oven to 325° F (160° C.) Grease and flour an 8 x 8 inch (20 cm) baking pan.
Dissolve the coffee granules in the teaspoon of water, stirring until there are no more solid pieces.
Add the flour, butter, salt, sugar and dissolved coffee to a large mixing bowl and mix with a spoon or by hand until all the ingredients are well combined and the color is homogenous.
Press the shortbread into the pan and bake at 325° F for around 50 minutes. Afterward, allow it to cool for 30-60 minutes. Loosen the edges of the shortbread from the pan with a table knife, then flip the pan upside down onto a plate. The shortbread should come out in one piece. Place it back into the pan before assembling the other layers.
Hazelnut Caramel Layer
Chop the hazelnuts and toast them at 350° F (180° C) for 10 minutes.
Add the caramels and the 1/2 cup cream to a double boiler or a heat-proof bowl placed over a pot of simmering water. Cook, stirring often, until the caramels are completely melted and the mixture is fully combined and smooth.
Remove the caramel from the heat and stir in the hazelnuts immediately. Spread the caramel mixture over the shortbread and allow to cool. To speed up the cooling time, you can put the pan in the freezer for 20 minutes.
Ganache Layer
If you are using a chocolate bar, chop it first and place it in a medium bowl. Heat the 1/3 cup of cream until it is right on the edge of boiling, then immediately pour it over the chocolate in the bowl. Let it sit for 30-60 seconds to melt, then stir until the mixture is smooth.
Spread the ganache over the caramel and allow to cool for 3-4 hours in the refrigerator before serving.