The use of coconut is optional. You can grind the whole wheat alone with little water and strain the mixture.
The quantity mentioned gives a thin drink, since my family loves this consistency. To make a thicker drink, reduce the milk by a cup and proceed with the same process.
You can skip the pearl onions and temper with only the fried cashews and raisins. However the onions gives it the actual Malabar flavor.
Instead of using only milk, you can use a mix of milk and coconut milk.