substitution: a key improvisational skill
ask: what job is this ingredient doing? who else can i hire to do this job?
The very first homework exercise for my in-person cooking class is “Make mustard cabbage without mustard and without cabbage.” I like it because it forces people to understand how the recipe works and then make substitutions that get to roughly the same place. The exercise makes people ask good questions: What really is the point of cabbage? What job is the mustard doing? Who else can I hire to do that job?
Recall how mustard cabbage works: we create a flavored fat by heating mustard seeds in vegetable oil. We arrest their burning by dumping in shredded cabbage. We cook the cabbage until it’s soft and fragrant, then cook it some more to brown it. We salt it to make sure we can taste all those flavors.
the mustard seeds’ job
Here’s a first shot at defining the mustard seeds’ job: they are there to flavor the fat. This job can be done by a bunch of other whole spices, powdered spices, herbs and aromatics. Cumin seeds would definitely work. So would fennel seeds. Would green cardamom? I predict that the result will be edible but not that yummy because cardamom is a strong and sweet spice which would likely overpower the delicately-flavored cabbage.
Ok so second shot: the mustard seeds are there to flavor the fat in a way that’s compatible with the cabbage. Some things go well together and others don’t. There are lots of rules of thumb about what goes well together: heavy, sweet spices go well with the strong flavors of red meat or kidney beans, lighter savory spices do better with vegetables or chicken or fish. These are helpful abstractions that attempt to predict the future, but they’re not always right. The more you cook, the more you’ll develop your judgement for what spices work with what veggies. Another way to figure out what combinations are compatible is by reading recipes. Recipes aren’t my favorite way to cook, but they can be very useful! They are notes from past chefs, ideas that worked. If two ingredients occur together in many recipes, they are likely compatible.
Fenugreek seeds are also, in my opinion, compatible with mustard. From South Indian cooking we get the idea of using uncooked dal — which are seeds — as whole spices. So you could fry some urad or chana dal in oil to create the flavored fat we need for this recipe. Both are very compatible with cabbage! How do I know that? Well, I know cabbage poriyal exists and has a subset of those ingredients. And I know that both urad dal and chana dal are nutty, savory and relatively subtle when used as whole spices. I’m trying hard to be more specific than “savory and relatively subtle” but it is legitimately hard to use words to describe flavors! It is perhaps a skill issue and I will improve as I write more.
What else? Sliced onion, chopped green onion, minced garlic, minced ginger, sliced green chili peppers, curry leaves, or any combination thereof would also work instead of mustard seeds for the job of flavoring the fat in a compatible way. Some of these ideas are from cabbage poriyal, others are from judging that these aromatics are “savory and relatively subtle”.
What about mustard-the-condiment? Totally works, and reminds me of eating sauerkraut (fermented cabbage) with bratwurst and mustard-the-condiment. That’s another example where knowing what has worked in the past is helpful when improvising.
the cabbage’s job
The cabbage exists to be, like, the main thing we’re eating. It provides bulk and calories. It also contributes its own idiosyncratic flavor, but that flavor is relatively light. It is substrate, vehicle, bass. The obvious replacement would be another brassica: kale, broccoli, brussels sprout, bok choy or collard greens (this is an example where knowing a tiny bit of botany can be helpful for cooking). Further afield, any leafy green can do this job well: spinach, swiss chard, beet greens.
What else is substrate, vehicle, bass? Potato! Or several other tubers and root vegetables, like taro, carrots, or sweet potato.
abstraction: taking the idea of substitution further
If you squint hard enough, a huge number of dishes across Indian, French, Italian and other cuisines contain mustard cabbage at their core, which is to say, they make a flavored oil and then cook something in it. This is a powerful insight, and it’s accessible through taking an existing recipe and asking questions like What is the mustard’s job?
Let me be more explicit. You begin with the idea of substitution: how do I make this recipe if I don’t have mustard seeds? You ask, What is the mustard’s job? You decide to use cumin seeds instead. That’s substitution. But then you say, Well, any way of flavoring the fat would also do the job. So you use onions and carrots and celery and you cook them down and maybe you let them brown a little. Or you use butter instead of oil, and you carefully and gently brown the butter, producing a nutty toasty flavored fat. Using browned butter instead of mustard seeds in oil can hardly be described as substitution. I’m a math/computer nerd so I find it natural to call this abstraction.