Over a decade later, Adler is back with the Everlasting Meal Cookbook: Leftovers A-Z—a guide on how to turn meager leftovers into new and tastier dishes that will appeal to everyone who prides themselves on making use of all the food they buy.

Adler’s creative salvaging knows no bounds. In her entry for almond butter is a recipe for “Empty Jar Nut Butter Noodles,” which you make by swishing hot water, fish sauce, lime juice, and some added ingredients around in a nearly empty jar of nut butter. Then, voila: You have a sauce for noodles! In fact, Adler’s section on ”empty containers” might just revolutionize how you use up the very last bits of everything from mustard to maple syrup.

Each chapter is devoted to a different food group or type of dish: vegetables come first, then fruits and nuts, then dairy and eggs, soup, salads, drinks, and so on. But within each chapter, Adler organizes each entry rather unconventionally by leftover ingredient. Under “Apples, old” she has recipes for apple cider vinegar, applesauce, apple scrap vinegar, and apple twigs (dehydrated apple peels, which makes a good children’s snack).

Under “mushroom soup,” she has a recipe for mushroom pasta sauce. Under “brine, mozzarella, or feta,” she counsels her readers in how to use the brine (with a little water and sugar) to marinade chicken thighs or pork chops in. Under “broccoli stems and leaves” she shares a recipe for garlicky stem and core pesto. And on and on.

A lot of the ideas in here are things our grandparents might have done without thinking—like baking fruit crisps with overripe or bruised berries, making croutons from stale bread, and rice pudding from day-old rice. But Adler, who is a contributing editor at Vogue, has done her readers an enormous service by recording these wise, frugal recipes in one place.

Nearly 40 percent of the food we buy gets tossed out, and that waste is responsible for a full 8 percent of all human-caused greenhouse gases. With that tragic reality in mind—and with food prices higher than ever—we spoke with Adler about her book, her philosophy, and some of her best tips for treating old and leftover food with the respect it deserves.

How did you get interested in salvaging older food? Not everyone is brought up that way.

It was a combination of influences. My mom was definitely a big saver and storer of things. We always had beans and rice cooked ahead in the fridge. She made croutons out of stale bread. So there was some osmosis, certainly. And the restaurants that I worked in were all really diligent about saving things. I think it is largely a misconception that restaurants are wasteful. It is true that when a diner doesn’t finish what they eat, it has to get thrown away. But cooks—if not restaurants—know what to do with everything [else].

A lot of the circular, ongoing, everlasting cooking is what feeds most restaurant staffs. So, I was exposed to it at Prune and at Chez Panisse. We kept things, re-used and repurposed—as much out of culinary motivation as environmental motivation. Most cuisines in the world do a good deal of saving, revisioning, and repurposing. I learned to look at food at various stages along its arc, because that is how you learn to cook Italian, French, and Middle Eastern food. I think when people don’t know [how to repurpose ingredients], it’s a gap in their education. I never thought of myself as a super scrappy saver person. It was just cooking.

You counsel readers to trust their senses. In the entry on moldy cheese you write, “I cut the moldy bits off cheese and taste what remains. If my visceral self revolts at what I’ve tasted, I sigh and discard. If it calmly bears up, I use what’s left as planned.” You also write about using spoiled buttermilk “unless it’s growing vicious green or blue mold.” Why do you think Americans are so quick to toss “expired” food out?

I think people do it because they are trying to protect themselves and their families. It hasn’t been made very clear that expiration dates don’t [typically] refer to the safety of food. [And “Best by” dates never do.] People are relying on something that is explicitly not designed to inform them about safety. That’s a problem with messaging. And it ends up working to the advantage of businesses that are selling food. People are forever throwing out things without actually contemplating what’s inside the containers.

What if instead of saying “May 14, 2023,” there were three recipes for what to do with your milk on your milk container? “If your milk starts to smell sour, here’s a biscuit recipe.”

I appreciate that you remind people to trust their palate throughout the book. We don’t have home economics classes in schools anymore, so we’re really just relying on knowledge passed on from family members or friends. 

I would like to have a help line! I would need a liability waiver—but I would be totally happy to get texts asking, “Is this okay?” at all hours. But I also think the visible food mold tends not to be the stuff that causes the really bad food-borne illness anymore. There have been huge recalls of ground beef, spinach, and romaine—and that’s not mold. Those are things that come through complicated supply chains—where there are lot of opportunities for contamination. So, we should be more scared of complicated and untraceable supply chains and less scared of things sitting out overnight. There are orders of magnitude of difference in risk. It’s totally understandable to not want to get sick, to not want your family to get sick. But it’s misdirected. We should be much more scared of these highly complex industrial supply chains and much less scared of aging food.

I know I should trust my visceral self, but now I’m going to pretend I’m calling your hotline. One thing I’m always wary about is already-opened canned tuna fish.  If it’s not moldy but it’s been in the fridge a week, is it still safe to eat?

Taste it! I don’t know when we started imagining that our taste buds were these precious temples that must never be transgressed. If I’m putting away canned tuna—I buy it packed in olive oil and make sure that it’s coated in olive oil, as that will help preserve it—I taste a little bit. If it tastes fizzy, compost it! If it doesn’t, eat it. Your mouth cannot be like this inviolable shrine!

What’s the worst thing that could happen?

You’ll spit it out! You’ll just spit it out. We can do that, you know?

Some of your recipes didn’t surprise me, but others, like leftover scrambled eggs for fried rice, broccoli stem pesto, and hummus soup, did. How did you come up with most of these recipes?

A lot of times I just adapted something that I’d eaten or tasted in some other environment or culture to whatever I had in front of me. A lot of it was seeing what is there as opposed to what is not there. Which sounds like a Zen koan, but it’s actually true. Maybe this is a particular form of optimism that is mine alone—but I’m conscious of the fact that there are so many ways to cook an egg and then combine it with other things. So if you just take the mental leap of, “I have already cooked the egg,” then you are halfway to whatever the next thing is.

I’m not sentimental—I just don’t like disposing of things. I imagine that everything has some kind of spirit or purpose. I’m looking for ways to use things, because they’re there and I care about them for being there. And I’m lucky enough to have a lot of culinary knowledge, which means I can make something good.

Another thing I love is that your re-use ideas extend to non-culinary purposes. Pistachio shells make good mulch, you suggest, or filler for the bottom of a potted plant. Peanut shells make good kitty litter. Pomegranate piths and skins can be dried and ground into a powder and made into a facial with yogurt. What other non-food uses might we have missed?

I have avocado pit and peel dye. Onion peel can also be used for dye. Obviously beet peels can be used as dye for cloth and Easter eggs. At one point I made lip gloss out of leftover Kool-Aid! But I cut it from the book, because I didn’t think leftover Kool-Aid was that much of a problem.

In the acknowledgements you thank a colleague for tasting all your creations and allow that bacon shortbread was perhaps a bad use of leftover bacon. Were there any other leftover-reuse fails?  

There were a lot of failures that didn’t make it into the book. I made something really bad out of melon rinds. I made a really gross kasha cake. I sent it to the recipe tester with a note saying, “This is mediocre.” And they wrote back, “I thought I was prepared for the mediocrity of this cake, but in fact, nothing could’ve prepared me for how mediocre this cake was.” So that went out. There was a donut bread—poached bread dumplings made out of cider donuts—that somebody wrote a scathing review of. I’m glad I tried them so you didn’t have to.

Throughout the book you talk about how much better things taste at room temperature and tell your readers not be afraid to leave things out. Why don’t we do this more in the U.S.?

It feels like the absence of a culinary culture, right? We’re following recipes to make everything as opposed to following traditions. My father was Israeli. We always had hummus, tahina, olives, pickles, and stuffed grape leaves sitting at room temperature for a long time. Lots of families that have emigrated from other cultures and have brought their traditions with them have at least one thing in their house that is like that. But that’s not necessarily true if you’re from an equatorial cultures, where food actually spoils at room temperature in a dangerous way. If you’re from a Caribbean country, that culinary culture is not going to involve leaving food sitting at room temperature, unless it’s heavily bathed in vinegar and that’s where escabeche (marinated fish) comes from.

Culinary traditions are about how to make things taste good and how to make gathering enjoyable for everybody; in the absence of that, there are rules. There are all kinds of rules that restaurants follow, for how cold things have to be and how hot they need to be. In the absence of culinary tradition, one turns again to what there is. But if you do have other input, because your family has a different tradition, you follow that. I’ve never had cold hummus in my house.