Chez CC, we tend towards the obsessive and completist bent so let's expound on it.
Let's start at the very beginning, a very good place to start — as Julie Andrews once sang.
What constitutes a spice?
It's a dried seed, dried root, dried bark, or dried vegetable/fruit whose primary role is for flavoring food. They rarely have nutritional value although most spices have considerable anti-microbial and anti-fungal properties which are an important reason that they are so heavily used. The other reason would be pleasure, of course.
There are at least 20-25 spices in the Indian repertoire and that's just what the CC can think of off the top of his head. There are at least 20-25 relatively more obscure ones. (Obscurity, needless to say, being relative.)
Simple combinatorial mathematics tells us that the number of combinations of these spices is going to be vast§ particularly when they are combined with other ingredients like nuts, souring agents, oils, etc.
There are eight basic techniques (and a bunch of auxiliary ones) that you need to master to really get a feel for the complexity of the subject.
On the first axis are the state of the spices. They can either be:
- Whole, or
- Dry-roast them.
- Fry them in oil.
- Soak in liquid overnight.
Classically speaking, if you were to take a class on Indian cooking, there would two techniques that would be emphasized — bhunaao and tadka (a.k.a. chaunk, baghar, etc.) Except that both of these are best understood as variations of exactly one of the eight. They are whole spices fried in oil. We'll come back to a discussion of these important techniques but it's useful to point out right now that both the two classical techniques fit into exactly one of the eight categories. Whole spices fried in oil.
There's seven more that we need to discuss in detail and that's even before we get to the variants of one of them. (Brevity only works if the subject can be distilled down into a brief summary.)
The biggest distinction is whether the spices are left whole or ground up into a powder.
When they are left whole, they will flavor the dish but they are meant to be left at the side of the plate when eating since they turn inedible. They give up their flavor to the dish but they are disposable. Smaller spices like cumin, caraway, sesame, etc. are edible but the larger ones are not. They won't do any harm just that it's not fun to chew them.
There is a reason that spices are stored whole. Spices mainly consist of a vast array of aromatic molecules which is what we love about them. The moment they are ground, we are increasing the surface area by an incredible amount and the volatile molecules start escaping. Even worse, the complex organic compounds start oxidizing. That's why pre-ground spices basically taste like dust. All the good stuff is long gone. There are a few exceptions like ground dried green mango (aamchur) and ground chili peppers (laal mirch) but they are the exception not the rule. (Really experienced Indian chefs will tell you that fresh red chilies have strong citrus notes but the dried and ground ones do not.)
The greatest gift of modern times to the art of Indian cooking is the simple coffee grinder. It makes easy work out of the hardest part which was pounding the living daylights out of spices in a mortar and pestle to get them to a powdered form. (Ironically, we lazy-ass modern-day soft-as-silk cooks can make far superior food compared to our rugged "hard-working" ancestors. Take that, bitches!)
Whole spices as-is generally apply to the smaller spices — cumin, caraway, nigella (kalonji), ajwain, sesame, fennel, etc. You get the taste the spice as it actually is.
Ground spices as-is is a common occurrence in desserts e.g. cardamom, nutmeg, etc. You will get a much stronger hit of the spice because of the surface area. You also see this in savory cooking with spices like dried ginger (saunth) and dried green mango powder (aamchur).
One of the two great techniques of Indian cuisine is dry roasting the spices. It intensifies their flavors. You dry roast the spices on a skillet in the order of size in order to prevent them from burning. As each spice is done, you set them aside to use individually or together as the case may be. This is a complex transformation and changes the nature of the spices. Cardamoms take on an intensity beyond the normal. Small seeds like cumin, caraway (shahjeera), and fennel will turn darker and far more intense. Black pepper will puff up and become even more aggressively black-peppery and cloves change shape and take on a dark fierceness. Mace (javitri) and dried cinnamon leaves (tej patta) turn pale brown and stronger in flavor.
The CC can't think of any dish that just uses the dry-roasted spices (but his knowledge is not infallible.) They are almost always ground to a powder. Almost all the masala's that you get commercially follow this pattern. They are dry roasted and ground. Learning how to do this in the right proportions is the single most important feature of Indian cuisine.
Soaking spices in liquid and using them is another technique. Traditionally, there are only two soaking agents — water and milk. Soaking mellows out the more aggressive notes of the spice and gives them a very subtle and rounded flavor. The milk used is almost always full fat since a lot of the compounds will dissolve in fat but not in water. The grinding is mostly done so that the larger more inedible spices can actually be eaten. (Yes, technically speaking, this is a paste not a powder. The CC gets it but the classification still makes sense.)
The same technique is used for nuts which while not technically spices are frequently treated by Indian cooks as being under the same umbrella. Both soaked nuts and soaked finely-ground nuts feature heavily in Indian cooking.
Why do the spices and nuts transform? Many of the spices and nuts are actually seeds so when you soak them in liquid, you are starting out the sprouting process which is a complex transformation and you get a different set of complex volatile compounds to work with.
While the spices soaked in milk would be ground with the milk, the nuts soaked in milk e.g. walnuts are drained and the milk discarded. The milk takes away the more aggressive bitter notes of the walnuts and makes them sweeter and more rounded.
One of the great technical pastes is that of poppy seeds soaked overnight in just a bit of water. The resulting paste is just absolutely superb. Stir-fry with a few other spices (cumin, whole red chilis) and almost any vegetable and you have a rocking dish.
The second great technique of Indian cuisine is to fry the spices in oil or ghee. Two things happen when you do this. You get the same effect as dry roasting because of the way frying works. In addition, the volatile compounds, which are generally soluble in oil, make the oil intensely flavored. When the dish is cooked with water in it, the emulsion of the oil and water brings out the spice flavorings. (Note that this would not be possible with just water because the organic compounds are typically insoluble in water.)
This complex change in chemistry means that this technique has a bunch of variants. One is to pan-fry the spices in the barest minimum of oil and then grind them to a powder. These various powders can be stored but not for long because the oil has a tendency to go rancid in the intense Indian heat. However, it will store in a dry cool place for about a year or the refrigerator which is the typical usage pattern of these ground masala's. (You will often see the use of nuts or dried coconut all ground with spices in masala's of this nature.)
The second is to pan-fry it with some oil until it just starts to stick and brown. This is the classical technique of bhunaao which is one of the most important arsenals in the repertoire.
Classical bhunaao is tricky. You use both whole spices and powdered ones. Generally speaking, the powdered ones are also dry-roasted first although this is not a given. You need high heat at the start to get the oil really hot but then you need to turn it down when the powdered stuff goes in and you need to stop right before the mixture burns by adding wet stuff. Experienced chefs add either a tablespoon of water to make it stop burning or wet ingredients like chopped onions. It's not as hard as it sounds but it does take some experience.
The last technique is to intensely heat up a small amount of oil in a specialized ladle. Whole spices are added to it and when they fry the entire mixture is plunged into a pre-made dish which is generally quite watery. This means that there's this wild theatrical aspect to watching sizzling oil and a hot metal ladle go into water which can be quite dangerous if you don't know what you are doing. This is the classical technique of tadka. The spices sizzle and pop dangerously in the oil but the final dish will be intensely flavored by the spices and the oil.
These techniques are not mutually exclusive. Many complex dishes rely on combinations of these three techniques. You may first fry a few whole spices in oil then cook the dish, and add some dry-roasted ground spices when cooking and finish off the dish either with a tadka or with more dry-roasted ground spices. The complexity of the layered flavoring comes from the interaction of these simpler techniques.
Indian cuisine has a seemingly infinite¶ aspect to it because of the sheer number of spices, combinations and techniques. However, almost all of it is reducible to just these eight ideas. The number of combinations is vast mathematically but it's possible to get a handle on the subject by approaching it in analytic fashion.
† The CC was sorely tempted to title this post The Eightfold Way but he refrained.
‡ All the other techniques of drying, roasting, frying, grilling, steaming. boiling, par-boiling, and baking are universal. These eight techniques were already enumerated in classical Sanskrit literature. The complex usage of spices is what sets Indian cuisine apart from the rest of the world.
§ Not kidding. We're looking at something like 240 (= 1012) combinations. Not all combinations will be tasty but even accounting for that we're looking at something like 109 combinations. As long as you live for a million years eating Indian food thrice a day, you'll get to try them all. Even in a practical way, there are at least a thousand combinations which will take you three years to get through. The "vast" part is not being exaggerated.
¶ Obviously, it can't be infinite.