The dictum “write what you know” may work in fiction, but if I had followed it in writing about food and cooking, I’d have put a gun to my head long ago. How soul-crushingly boring it would be simply to transcribe information you already knew.

I write to discover. I write to understand what I think.

I didn’t write Charcuterie because I was an expert in the craft. I certainly didn’t do it for the money—a love song to animal fat and salt in a salt-and-fat–phobic country, a book with recipes that take hours, days, even months to prepare, and if you do them wrong, botulism can kill you? “Oh yeah,” publishers cried, “we want that one!”

I wrote Charcuterie because I knew nothing about it, and I was compelled by its premise: that methods once used to preserve food to keep us alive happen to result in some of the most sublime food we know. (The book has now sold more than 150,000 copies and has the unconfirmed distinction of being the most stolen cookbook in America.)

This method of writing about what you don’t know leads, perhaps inevitably, to single-subject cookbooks. I am excited by ideas not recipes. Recipes are a dime a dozen, we are floating in a sea of recipes, carried willy-nilly by the tide. Ideas, though, you can get inside and drive.

What is it about the idea of schmaltz, chicken fat rendered with onion, that has made it such an evil in the Jewish kitchen (“early-grave food,” it’s called); how can this fat, arguably better for you than butter, be so maligned and all but invisible to the American cook? I’m 100% goy, so I turned to my neighbor, Lois Baron, an Ashkenazi Jew schmaltz aficionado, and began The Book of Schmaltz.

Even my general-technique cookbook, Ruhlman’s Twenty: A Cook’s Manifesto, is basically 20 single-subject book proposals. One of which, Egg, expanded in my mind with such profound significance that, when the manic exaltation of discovery subsided, I created a flowchart. Egg, cooked in shell or out of shell? If in-shell, then hard or medium or soft or sous vide? If out of shell, whole or blended? If whole, then fried or poached shirred or coddled? If blended, scrambled or baked? And on and on it went—through cakes and batters and emulsified sauces—till my wife and photographer, Donna, had mapped out on five feet of parchment the complete egg flowchart.

How many editors get a book proposal on one five-foot scroll of parchment?

Indeed, the single-subject cookbook is potentially the most important type of cookbook published—a thought I’d never considered before being asked to write on this subject.

I believe that our lives and our world become a better place when we cook our own food and share in the work and the eating.

But we are pressured from every direction to avoid cooking. We’re too busy. We’re taught that cooking from scratch is too hard. Thus my goal has always been to simplify and clarify cooking. I do this first with ideas. The recipes are simply support material, evidence of abstract ideas brought to nourishing life, with eggs and butter, fat and salt, flour and water.

All preparations are based not on ingredients and techniques, but rather on proportions of one ingredient relative to another—“It’s all one thing.” Bread dough and crepe batter are at either ends of the same continuum; they’re connected, and when we understand that idea, bread and crepes, and everything in between, are easier to cook.

So in the same way that there are no new stories, I am simply writing the same cookbook over and over, in which the task is not to create something new, but to deepen our understanding of what is already known.