Place flour, salt, sugar and cocoa in a food processor.
Pulse a few times to combine.
Add butter and pulse until it looks like coarse breadcrumbs.
Add egg and pulse until large crumbs form.
Turn out dough onto a lightly floured surface and bring together.
Form disc, wrap in cling film and place in the fridge to rest for 20 mins.
Roll out dough to about 3-5mm thickness and line pie tin. Push pastry into the corners and fluted edges then trim off the excess pastry.
Cover with cling film and place in freezer for 30 min to firm up.
Dock the pastry with a fork then bake blind for 20min, then remove beans and bake a further 10 min.
To make the salted caramel, bring the sugar and water to a boil in a saucepan and cook until golden brown in colour.
Remove from the heat then add the cream carefully. Mix until smooth then mix in the butter, one cube at a time, macadamias, vanilla and salt.
Pour into the baked tart shell then place in the fridge to set.
To make the ganache, warm the cream to boiling point (take care not to boil the cream) then pour over the chocolate. Stir until the chocolate is completely melted then pour over the salted caramel layer and place back in the fridge to set.
Pipe the white chocolate into spiderweb patterns onto parchment paper and allow to set in the fridge.
Decorate the chilled and set tart with the white chocolate spiderwebs and plastic spiders.