Pre-heat your oven to 160C Fan/180C/350F/Gas Mark 4
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 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
Bake the biscuit base for 10 minutes, take out and set aside to cool
Mix the salt into the caramel (if it's not already a salted caramel sauce) and pour into the biscuit base
To make the ganache put the double cream, dark chocolate and butter into a pan and melt together on a low heat until it becomes a rich glossy chocolate sauce
Pour the chocolate sauce into the biscuit base over the caramel, put the tart in the fridge for at least 2 hours to set
When ready to serve, whip up the double cream decoration and spoon onto the tart. Then use a potato peeler to grate dark chocolate shavings over the top
Serve immediately. Store leftovers in the fridge and eat within 2 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.
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.