Besan, also called gram flour, does more batter work than any other flour in a chaat and snack kitchen. It is also easy to get wrong, because it has to behave differently depending on what you are cooking. The batter that coats a pakora should be thick and clingy. A batter for steamed dhokla should be light and slightly aerated. And a khandvi batter must be loose enough to spread almost translucent on the counter, yet still set firm once it is cooked. Nearly every besan failure, whether a soggy pakora, a dense dhokla or a khandvi that won't roll, goes back to the wrong consistency or rest time for that dish. The flour itself is rarely to blame, so look at your batter before you blame the bag.
Keeping lumps out from the start
If your batter is full of small hard lumps, the water probably went in too quickly. Fine flour at the edge of a clump soaks up liquid and forms a skin, and the skin traps dry flour in the middle. To avoid it, whisk the besan with spices or salt while it is still dry, then add water a few tablespoons at a time, whisking constantly, and don't pour it all in at once. Sifting the besan beforehand removes any clumps already there, which helps a lot if the flour has sat in its container and compacted. If lumps still form, push the batter through a sieve using a spoon. That works better than whisking, which often just breaks big lumps into smaller ones instead of dissolving them.
Pakora batter, the coating consistency
Pakoras and bhajiyas need a batter that grips the vegetables and leaves a visible, even coat without running off into the pan. Think of a thick pancake batter. Raise the whisk, and the batter ought to slide back into the bowl in a slow ribbon, not a thin trickle. Too thin, and the coating fries into a weak, see-through shell that never crisps. Too thick, and the pakoras turn doughy and underdone in the middle before the outside browns. Stirring a little rice flour or cornflour into the besan, up to about one part in five, gives a noticeably crisper result than besan alone, because it fries lighter and is less likely to soften as it cools. Let the batter stand for 10 to 15 minutes before you fry so the flour hydrates fully. That also helps the coating stay on wet or oily vegetables, and it gives you time to heat the oil properly.
Dhokla and khandvi batter, thinner and smoother
Batter for steamed dhokla is much thinner than for pakoras, closer to a pourable, medium-bodied crepe batter. It has to settle evenly across the steaming tin and lift with the help of a leavening agent, either the quick fruit-salt-and-eno shortcut or a longer fermented method. Khandvi batter is thinner again, nearly like milk, because it is poured onto a flat surface in a very fine layer and has to firm into a bendable sheet while cooking, with no rising or puffing. Try this with khandvi: cook one small spoonful on a plate and see whether, after about a minute, it is firm enough to roll without splitting. If it is still tacky or won't hold a roll, keep cooking it, or make the next batch a little thicker. A batter that is too thin never gains enough body to lift cleanly from the plate.
Judging consistency by eye
You don't need a measuring jug to judge besan batter, only your eyes and a spoon. Three pictures in your head cover nearly every use. The first is the ribbon: batter falls from the spoon in slow folds that sit on the surface for a moment before melting back in. That suits thicker dhokla batters and some stuffed pakora coatings. The second is the coat: batter stays on the back of the spoon as an even, opaque layer and doesn't slide straight off, which is what standard pakoras want. The third is the pour: batter leaves the spoon in a thin, steady, nearly unbroken stream, which is right for khandvi and thinner dosa-style besan preparations. Hold your batter up against these before you fry or steam, and you will waste far less than if you try to repair a bad batch afterward.
Rescuing batter that is too thick or too thin
Thick batter is the easier problem. Add water a tablespoon at a time and whisk in between, because besan batter thickens unevenly and it is easy to overcorrect. Thin batter is harder, since stirring in more dry besan risks bringing the lumps back. Instead, whisk a little besan with a splash of water in a separate bowl until smooth, then fold that paste into the main batter. That paste mixes in much more evenly than dry flour tipped straight into the bowl. If a resting batter has thickened by itself as the flour keeps absorbing liquid, that is normal. Besan batter nearly always needs a small water adjustment right before use, even when it looked right as first mixed.
Salt, acid and the timing of fermentation
When a besan batter relies on fermentation or a quick leavening reaction, and not on steam alone, for lift, salt and acid both affect the timing. Salt added early can slow fermentation slightly, because it pulls moisture out of the batter and tightens gluten-like protein structures in the besan, so some cooks keep the salt back until closer to cooking when the batter will ferment for several hours. Acidic additions, such as a spoon of yogurt, or lemon juice in a quick-leavened dhokla batter, bring on a stronger reaction with baking soda or fruit salt, and the bubbling is faster and livelier. That is handy when time is short and you still want a lighter crumb than plain batter would give. After a few hours at room temperature, a fermenting batter should look a little puffed and carry fine bubbles on top. If you see no change after many hours in a warm kitchen, the leavening may be dead or the room too cool, and gentle warmth is usually a better fix than waiting longer.
Resting and holding batter
A short rest helps nearly every besan batter. Allow about 10 minutes for a simple pakora mix and 20 to 30 minutes for dhokla. During that time the flour takes up its water fully and the finished dish comes out smoother. If the batter has stood for a while, particularly in a warm kitchen, whisk it again and adjust with a little water just before cooking, because besan keeps absorbing liquid and settling as it sits. Leftover pakora-style batter does not keep well past a few hours at room temperature. If it has to wait, refrigerate it, then bring it back to room temperature and re-whisk it before frying.