Start by prepping your coffee soak. In a medium-sized jug, mix together the coffee granules and boiling water until the coffee granules have dissolved. Set aside to cool completely.
For the filling: in a stand mixer fitted with the whisk attachment (or a large bowl and electric whisk), whisk together the mascarpone, double cream, caster sugar, vanilla bean paste and pistachio cream on medium speed until thickened and holding its shape. This should take a few minutes, but watch closely as you don’t want to overwhisk or it will go grainy.
Next, using a bread knife, slice the panettone into rounds - you could do 2,3 or 4 depending on the shape of your panettone. I normally do 3.
To assemble: place the bottom layer of panettone on a large flat plate or cake stand (make sure it can fit in your fridge). Generously brush with the cooled coffee - you want a good coating to add flavour, but not too much as to make it soggy. Then spread with 2 tbsp chocolate and hazelnut spread. Dollop over the creamy pistachio filling and spread in an even layer (if making 3 layers, use half the mix). Repeat the layers.
Top with the ‘hat’ of the panettone. Cover and chill in the fridge for at least 2 hours, ideally overnight. This will enable it to firm up and become easier to slice.
For the meringue (optional): If you don’t have a blowtorch, preheat the oven to 260C/240C Fan. In a stand mixer fitted with the whisk attachment (or a large bowl and electric whisk), whisk the egg whites until foamy and bubbly. Gradually, a tablespoon at a time, whisk in the soft light brown sugar. Make sure the previous tablespoon is completely whisked in before you add the next. Continue to whisk until the sugar has dissolved and you have a smooth and glossy meringue. If you pinch a little of the meringue mixture between your fingers, you shouldn’t feel any grains of sugar.
Using a palette knife, spatula or the back of a spoon, spread the meringue all over the tiramisu cake.
To caramelise, use a blowtorch to caramelise the top and set it slightly. Alternatively, pop in the preheated oven for a few minutes until the outside has turned a deep golden brown - watch closely to make sure it doesn’t burn. You also don’t want to leave it too long or else the inside will get hot and the cream will melt.
Serve straight away!