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Compost potatoes might be José Andrés’s ‘most insane recipe’ yet. Here’s what they taste like.

The recipe, one of the first to appear in José Andrés’ newest book, “Vegetables Unleashed,” was “conceived in a fit of passion,” the chef wrote.

It has only four ingredients:

  • Potatoes
  • Kosher salt
  • “Used coffee grounds”

[Huh, okay.]

  • “Vegetable scraps from your compost bin.”

[Excuse me, what?]

It’s called “Compost Potatoes,” and he might be correct when he writes: “This might be the most insane recipe I’ve come up with.”

José Andrés wants you to cook your potatoes in garbage. He has his reasons, and they are noble: It’s a statement on food waste. Compost potatoes are about taking something that’s “about to go to waste, and we are giving it one more service to humanity,” Andrés said. I mean, the guy is a national hero. And the recipe sends a very good message to a population that wastes a quarter of all the food we buy.

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Still. Compost? The slimy stuff you shovel in a heap in your backyard? We say this with the utmost respect: José, what the heck is going on here?

Here is how Andrés describes the genesis of this recipe in his book: “I had the last of some beautiful Peruvian Blue potatoes from my garden staring up at me from the countertop. Almost without thinking, I reached for the coffee filter in our drip machine and dumped the spent grounds into a roasting pan, then laid the potatoes over them and emptied my compost bin on top. It sounds crazy, but it makes sense: it was the same compost that goes into my soil where those potatoes grow.”

He calls for readers to “nestle” the potatoes into an undetermined amount of coffee grounds, and then cover them with “a few scoops from your compost bin (avoiding anything too wet, like tomato pulp or cucumber seeds).” Bake the potatoes for one hour at 400 degrees, and then peel and serve them with some garlicky mojo verde, or romesco, or just salt.

In a footnote, Andrés’ co-author Matt Goulding seemed to recognize some of the mental hurdles that must be overcome to make this recipe. “When you catch José in the middle of a special moment, there’s little you can do but stay out of his way,” Goulding wrote. “And so it was with these potatoes roasted in compost — at first blush, not especially appetizing, but not without their charm.”

The subtext was not lost on the chef. “If you read the bottom, he’s almost like saying, ‘José imposed this recipe on me,'” Andrés said.

A note on language here: The word “compost” typically refers to “decayed organic material used as a plant fertilizer.” Decayed organic matter is almost certainly something you would not want to cook with.

“Pathogenic bacteria represent the biggest risk” in cooking with actual compost, said Martin Bucknavage, senior food safety extension associate for Penn State University, via email. “The types of organisms present would be dependent on what the raw materials of the compost are and the state of the compost,” but they might include some really bad ones: “Pathogens of concern include salmonella, pathogenic E. coli, Campylobacter and listeria.” Yikes.

But even though Andrés’s recipe says compost, what he’s actually putting on his potatoes is a sort of pre-compost. It’s vegetable scraps from his kitchen — things such as wilted spinach, eggplant tops, carrot peels and the outer leaves of leeks — that haven’t yet been mixed with grass, leaves and dirt. They’re the little scraps that a person could freeze and use to make vegetable broth, or put in a small countertop bin to empty in the compost the next morning. The day Andrés developed the recipe, he said he had corn leaves and husks. During our conversation, he texted me a photo of his countertop bin, which appeared to be full of coffee grounds, banana peels and orange rinds. It hadn’t been sitting out too long; the banana peels were still relatively yellow. He said he empties the bin once a day.

“People often say compost instead of food waste. They’re totally different things,” said Rhonda Sherman, a composting specialist in North Carolina State University’s horticultural science department. “It might have been a little reckless to say that,” because if someone used actual compost, they might get sick.

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But just using your kitchen scrap collection bin doesn’t eliminate the risk, either. It depends on the condition in which those vegetables were grown and how long they have been sitting out.

When food sits out, “Every 20 minutes, bacteria doubles,” said Jeff Nelken, a Los Angeles-based food safety consultant. “Anything coming out of the soil has an exposure to bacteria.”

And given that vegetables have been the source of several major outbreaks — romaine lettuce was pulled from stores for E. coli last April, and salmonella has been linked to leafy greens and melons — you don’t know what might be on your vegetables.

As for the hour they’ll spend baking: Nelken says that 400 degrees would be enough to kill those pathogens, but cautioned that ovens are imprecise. Just because an oven says 400 degrees does not actually mean it has achieved that temperature, much less that all of the food has gotten up to temperature, too. There are hot and cold spots in ovens. He recommended using a thermometer to check parts of the dish, but really, he recommended sticking with some of the less worrisome recipes in Andrés’s book. How about some nice fried eggplants with honey, or some yakitori Brussels sprouts, or a lovely Castilian garlic soup? If you want to make compost potatoes, “proceed at your own risk,” Nelken said.

Andrés knows that vegetables have been connected to various outbreaks. “At the end of the day, safety is first. That’s why we all need to know where our foods come from,” he said. But in his personal consumption, he’s less concerned about those pathogens, because he gets all of his vegetables from trusted farmers, or from his own vegetable garden or indoor greenhouse. He makes the compost that fertilizes his vegetables. His dirt is so good, he says, that he has eaten his vegetables directly from the ground.

“Until you [have eaten] a potato directly from the soil, you have never tasted a potato you like,” he said.

He’s wary of the compost wariness that he rightly predicted this article could bring.

“Compost will not kill America. Compost will make America stronger and cleaner and richer,” he said. “We cannot survive without good compost. The future of our land depends on good nutrients.”

Andrés isn’t the first chef to experiment with compost. Bon Appétit wrote about a New York restaurant (granted anonymity “since it’s still working out the legality of the whole thing”) that would cook meat inside heaps of compost in a strange version of sous vide. Compost heaps can reach internal temperatures of 160 to 170 degrees, and the chef stuck a ham in there — presumably wrapped in plastic, as other compost cooking evangelists have done it. That method is more about the heat generated by the pile’s decomposition, rather than the actual flavor of the compost, which never touches the food.

Andrés recalled a dinner where he roasted a squab in dirt and compost. He also mentioned that his friend, renowned Spanish chef Juan Mari Arzak, distilled alcohol with compost in an alembic. “He got an essence of compost that was very aromatic,” Andrés said. Arzak’s daughter, chef Elena Arzak, has made mushrooms cooked in a compost crust.

“An essence of compost that was very aromatic” would be a polite way of describing the scene in The Washington Post food lab when we tried the recipe.

We got a container of used coffee grounds from our nearby Compass Coffee. And our vegetable scraps came from a busy day in the food lab — we let them sit together in an open bag overnight — and from editor Joe Yonan’s own kitchen compost container (which hadn’t been emptied for several days).

The veggie scraps had the distinct smell of decay. They weren’t rotten yet — everything was in pretty good shape, to be honest — but they smelled exactly like you’d expect some vegetables on the verge of composition to smell. When we pulled them out, we retched a tiny bit.

And then we followed the instructions: A few generous scoops of coffee grounds on the bottom of the roasting pan, and eight Yukon Gold potatoes nestled within. Beyond the recipe’s virtuous symbolism, its first steps are visually appealing. The coffee grounds look almost like dirt — the dirt from which Andrés pulls his immaculate potatoes — and there’s a certain loveliness in that. But then you layer it with long-wilted radicchio, and some soggy bits of leeks, a brown avocado peel, some lettuce that is way, way past its prime, and other odds and ends. (We also made a version with fresh veggie scraps, as a control.)

As it roasted for one hour, the kitchen filled with the twin aromas of stale coffee, and a scent that reminded us of that bag of spring greens you forgot was in the back of your fridge, until you open it and realize that the bottom leaves have all gotten a little bit slimy.

This was apparently not the case for Andrés.

“If you smell [compost], it is like a great perfume,” he said. “I think of compost as something very sexy; something nice, beautiful. You want to be a part of the smell of compost.”

When the potatoes came out, we peeled them and took a bite. The side of the potato that touched the coffee grounds tasted like stale potato coffee. The side that touched the compost tasted like a regular potato. We also ate them with the optional mojo verde, a garlicky parsley sauce, and it was an improvement.

“There will be some people who always have to be on the negative. They would say, ‘That’s nuts,'” said Andrés, who is so eager for people to make the recipe that he told me to encourage people to tag him in their photographs of it. “I would say, putting ketchup on everything is nuts.”

Look, it’s not like we’re against composting, or creative reuse of food waste. But let’s just say we wished we had stuck those scraps in the freezer and had used them to make a vegetable stock instead. That’s what happens when a recipe is also a metaphor.

“I think the recipe works in a way that it is food for thought,” Andrés said.