Soak almond and pistachio over night and peel the skin in the morning.
Soak poppy seeds and melon seeds for about 2 hours in little water.
Soak fennel seeds, cardamom and pepper corns in some water for 2 hours.
Grind together almonds ,pistachio,poppy seeds and melon seeds with some water and make a fine paste.now add the gulkand and grind again.
In a pan add sugar and a glass of water and cook on medium heat to make a sugar syrup of 1+ 1/2 thread consistency.
Add 2 tsp of milk in the boiling syrup to remove the scum floating on top.
Now add citric acid and mix then remove it from the gas and let it come to room temperature.
Add the ground almond paste in the sugar syrup and mix well.
Grind the fennel seeds ,cardamom and pepper corn with water and make a fine paste.
Add the fennel paste and the soaked saffron in the sugar syrup and mix .
Now just give a boil to the sugar syrup after mixing all the ingredients in it.
Now strain the hot syrup with a muslin cloth or a strainer and then let it come to room temperature.
Now add rose water and fill it in the glass bottles and keep refrigerated.
How to serve- Take about 3-4 tbsps of thandai concentrate in a serving glass add some chilled milk/water/juice and some ice cubes ,mix and serve.