Preheat the oven to 200°C/400°F.Using a pair of scissors, cut the puff pastry into thick, long pieces, then squares and finally in triangles. You don't have to worry too much about getting the sizes similar.
Place the pastry triangles onto non stick baking sheets and bake them for 15 - 17 minutes until they've puffed up and crisped up. They should be a medium golden brown colour.If your oven runs hot, check at the 13 minute mark.
Heat the Milk
Place both milk in a small saucepan and place on medium-low heat. Add the sugar and cardamom and bring to a simmer. Stir the milk to dissolve the sugar.Keep a close eye on it as you don't want it to boil over.
When the sugar has dissolved and the milk is very slightly simmering, take it off the heat and set aside.
Assemble the Om Ali
Take your baking dish and place half the baked puff pastry in the dish. Don't worry if you have to do 2 layers, as long as your dish is deep enough. It wants to be about 7.5cm/3" deep.
Sprinkle your nuts and mixed fruit all over.
Stir the rose water into the milk and pour this milk mixture all over the puff pastry.We add the rose water once the milk is no longer steaming hot, so that the aroma doesn't float up along with the steam.
Top with the rest of the puff pastry.
Using a ladle or spoon, lightly press down your puff pastry to allow them to soak up some of the milk. Only slightly, say the bottom half of the first layer of pastry triangles.Your om ali can be made ahead up to this stage and kept for 3 hours at room temperature before baking. The pastry will absorb quite a bit of the milk though. You can add a little more milk just before baking if you like.
Lightly whip the mascarpone or eshta (whatever you are using) with a fork to loosen. Then drop large spoonfuls of it over the top layer of pastry. You don't want to cover all of it as you want to leave crispy bits of pastry.
Bake in the oven for 15 - 20 minutes until the sides are bubbling and the top has turned a deep golden brown.Serve immediately if not going on to the next stage. Be careful, it's hot!
Caramelised Sugar Layer (Optional)
Sprinkle 1 Tbsp of sugar all over and using a kitchen torch on medium-low, go over the sugar to caramelise it. You'll probably burn tiny bits of pastry but this adds to the flavour.Or place it under a medium grill for about 3-5 minutes.Serve immediately.