First make the syrup by mixing all the ingredients except the honey, in a small saucepan. Once boiling, lower the heat and simmer for 5 minutes. Remove from the heat and add the honey. Allow the syrup to cool completely.
Preheat the oven to 160 C. Butter a 25 x 35 cm oven proof dish with the melted butter.
Separate the kadaif pastry strands and mix well with the melted butter. Put it in oven proof dish and spread it out to cover the base. Bake for 55-65 minutes until it is golden brown. Remove from the oven and pour the cold syrup over it. Allow to rest for about 30 minutes.
Make the pastry cream. Put 1 cup of the milk in a bowl. Add the corn flour to the bowl and stir to dissolve. Place the remaining milk, cream and the sugar in a saucepan over medium heat. Bring the mixture to a simmer.
Put the yolks, whole eggs, the vanilla and corn flour into a large bowl. Whisk to combine. Slowly pour the warm milk into the egg mixture, whisking constantly. Transfer the entire mixture through a sieve, back into the saucepan and add the crushed mastic. Whisk over medium heat until the mixture thickens and begins to bubble. Stir quickly for 1 minute and remove from the heat. Add the butter and stir until melted and incorporated.
Pour the cream over the kadaif, spreading evenly. Cover with plastic wrap which should touch the surface of the cream to prevent it from forming a skin. Allow to cool completely. Transfer the dessert to the refrigerator to cool thoroughly.
Whip the cream with the icing sugar and vanilla until thickened. Spread over the cooled pastry cream and sprinkle with pistachios.