In a large bowl, beat the egg yolks with the sugar and honey until pale and frothy.
In a saucepan, stir together the milk and saffron and bring to a simmer over medium heat.
Gradually whisk half of the hot milk into the beaten egg yolks in a thin stream, then pour this mixture back into the saucepan into the remaining milk.
Cook over moderately low heat, stirring constantly with a wooden spoon until a custard forms thick enough to coat the back of the spoon. Be careful, don’t let it split.
Pour the custard into a bowl over an ice bath and let it fully cool, stirring occasionally.
Whisk together the cream, rum (if using) and vanilla to soft peaks then fold through the cold custard. Pour into a glass container, cover and freeze overnight.
To make the pistachio crumb
Preheat the oven to 160°C and line a baking tray with baking paper and set aside.
In a medium-sized bowl, combine the finely processed pistachios, flour, sugar together with a wooden spoon.
Add the butter to the bowl and combine. Create small ‘crumble-lumps’ by rubbing the butter and flour mixture between your fingers.
Spread the crumble mix and roughly chopped pistachios evenly onto the baking tray and bake for 5–10 minutes or until golden. Set aside to cool.
Sprinkle crumble on top of the ice cream and enjoy.