To make the base use a food processor to whizz up the digestive biscuits into crumbs, or you can put them in a bowl and bash them gently with a rolling pin
Mix the melted butter into the biscuit crumbs and press them into a loose bottomed 23cm/9" tart tin covering both the base and sides. Put the biscuit base in the fridge for 30 minutes to set and firm up
For the filling, melt the butter in a pan and chop up the kadayif pastry. Add the pastry to the pan and cook until golden and toasted all over. This will take 10-15 minutes on a medium heat and you should stir it regularly
Mix the pistachio spread into the pastry while it is still warm and add the salt too. Spread the mixture out into the biscuit base in an even layer
To make the chocolate ganache, warm the double cream up in a pan on a low heat, give it a stir regularly. Take the cream off the heat when it starts to steam. Add the chocolate to the cream and leave it for a couple of minutes, then stir until it all melts together
Pour the ganache into the biscuit base over the pistachio and pastry mix. Gently spread it out and smooth the top using a small palette knife. You can also tap the tin very gently on the work surface to even out the ganache and remove any air bubbles. Put in the fridge for at least 4 hours, or ideally overnight, to set
When ready to serve, remove the tart from the tin, whip up the double cream with the icing sugar and vanilla extract and pipe it around the edges of the tart. Drizzle the tart with the pistachio spread (warm it for 10-20 seconds in the microwave first to make it pourable). Then sprinkle over the chopped pistachios
Serve immediately. Store leftovers in the fridge and eat within 2-3 days
Notes
You can use either butter or a baking spread for the biscuit base.
I recommend using good quality chocolate for the ganache filling for the best flavour and most accurate results. Avoid using cooking or baking chocolate.
Make sure to use double cream for the ganache filling, single cream will not work.
If you can't get hold of the kadayif pastry, you can omit it and just fill the tart with pistachio spread only. Or you can use something else like crushed Shredded Wheat to replicate the texture.
Although I provide cup measurements, I highly recommend weighing your ingredients out using digital kitchen scales. It is the most accurate way to measure ingredients and will ensure the best results. Digital scales are very low cost and can be purchased for around £12 ($16.50).
For teaspoon (tsp) and tablespoon (tbsp) measurements, please use measuring spoons and not the type of spoons you eat with. Again this will ensure accuracy and provide the best results.