https://www.gujrasoi.com/2021/05/cold-coco-of-surat-chocolate-milk.html
Here is a simple recipe for making a classic hot cocoa:
Ingredients:
2 cups milk (can be any kind, including almond or soy)
1/2 cup granulated sugar
1/3 cup unsweetened cocoa powder
1/4 cup dark chocolate 60%
1/4 tsp vanilla extract (optional)
Pinch of salt
Whipped cream or marshmallows (optional, for garnish)
Instructions:
In a medium saucepan, whisk together the milk, sugar, cocoa powder, vanilla (if using), and salt.
Place the saucepan over medium heat and bring the mixture to a simmer, whisking constantly.
Once the mixture comes to a simmer, reduce the heat to low and continue to cook, whisking occasionally, for an additional 3-5 minutes, or until the cocoa and chocolate is hot and the sugar has dissolved.
Remove the saucepan from the heat and pour the cocoa into mugs.
If desired, top with whipped cream or marshmallows before serving.
Note: You can also add some chocolate chips or chunks to the recipe to add more chocolate flavor. Enjoy!
So the conclusion, the Surat cocoa is made using milk, cocoa powder, sugar and little thickener like custard powder, which keeps the smoothness intact and the real coco is made using the actual chocolate and coco powder.