Add 1 cup of water and one cup of sugar to a small sauce pan. Cook in medium flame for 12- 15 minutes till the sugar dissolve and the syrup gets little sticky. If you touch the syrup it should feel little thick and sticky. Do not over cook.
Add 3 cups of milk to a heavy bottomed pot. Cook the milk for 10-12 stirring often. The milk would have slightly reduced.
Now add ¾ cup mawa (not sweetened), ½ cup + 2 tablespoon sugar, a generous pinch of saffron and cook till the milk mixture becomes semi thick. At this point taste the rabdi for sweetness and add more sugar if desired. Add crushed almonds and cashew and cardamom and cook for another 5 minutes.
To assemble the shahi tukda, make sure the sugar syrup is hot. If not just heat it for 1-2 minutes. Now slice the croissant to half, and dip the bottom of the croissant in the sugar syrup just for 3-4 seconds and place it in the tray.
Repeat with rest of the bottom part of the croissants ( see the pic for reference). Pour some of the hot milk on top of the croissants.
Now dip the top of the croissants with the sugar syrup and arrange it in the tray. Keep one cup of the rabdi aside and add rest of it on top of the croissants. Press it slightly and microwave the tray for 3 minutes. Add some mawa (optional) on the top. Press it down. Cover and let the mixture rest for 1 hour on the counter.
After an hour the croissants would have absorbed most of the milk. With a spatula press the croissants and add rest of the rabdi on the top. Cover and refrigerate over night.
Garnish with edible silver vrak and crushed pistachio.
Remove it 1 hour before serving.