Start with the lesser quantity of water. Once the batter is ready, add more water as per need.
The quantity of the water depends on the flour, so go with your instinct.
Do not use hot water for preparing batter. If required, use lukewarm water in the worst case only.
Hot water will start to caramelize the jaggery, and malpua will turn chewy and hard.
Traditional recipe follows - 1:1 ratio for flour and jaggery. So for cup measurement, 1 cup flour: ½ cup jaggery works well.
Ferment the batter for at least 5-6 hours. So plan accordingly.
Always prepare one malpua and do a thickness test. Then adjust the final consistency. Because in malpua batter, after the fermentation, you can not add dry flour. It may change the taste and texture of the final dish.
You can add seasoning as per taste or skip them.
I prefer to add the whole peppercorn so one can remove them if one doesn't like them.
Fennel seeds give a nice crunch and the taste of malpua.