One evening, while Chef Matt Haase was working at Kil@wat, he came up with a new dish – Cobia served with an Indian inspired shellfish broth, roasted carrots and radishes and puffed forbidden rice.

The dish was augmented with pickled orange rind and another ingredient that may have given some diners pause.

Leek ash.

Like many of his contemporaries, including Chicago's renowned Grant Achatz and Frank McLeod from Lespalier in Boston, Haase was breaking new ground.

He grilled the fibrous leek tops until they were charred and then slowly dried them out in the oven. Their bitter, slightly smoky flavor bolstered the sweetness of the carrots and rounded out the complexity of the dish.

But, where did the idea of using ash to enhance the flavors of a dish come from?

As with most trends, it's a modern spin on an ancient practice.

Largely due to chemical properties that make it an asset in food preservation, ash has been a part of food culture for centuries. Mexicans have used it in the processing of corn, cooking the grain in water mixed with ash. Europeans have favored it in cheese-making to help develop a rind.

Today, ash is still most commonly used as a preservative and flavor enhancer for cheeses like Humbolt Fog, Morbier and Valencay. But, more recently, edible ash has become part of the tool kit for contemporary chefs.

According to Haase, Spanish-born chef Ferran Adria reinvented the usage of edible ash in the late 1990s when he presented a dish called "vegetables on the grill," small terrines of juiced vegetables set into jellies, then seasoned with charcoal oil. That dish was the first time jellies were served hot.

From there, the trend took off, slowly making its way up and down the coasts, and eventually into the Midwest.

Since the flavor of ash can vary widely – producing overtones that vary from charred, to acidic, to sweet or smoky – the technique is versatile and can be used to bring a broad range of flavors out of a dish. That said, it doesn't mean the flavor is always appealing to everyone.

Haase tells me about "Turtle Sundae version 1.0" a creation he worked on with Kurt Fogle, pastry chef with SURG Restaurant Group, featuring Manjari cremeux, salted caramel, pecan crumble, and charred oak ice cream.

"We took old used bourbon barrels and charred them, steeped them in ice cream base and added bourbon," Haase says. "Kurt's idea was awesome, but only half the guests that tried it liked it."

At Circa 1880, Chef Thomas Hauck takes a different approach. He uses vegetable powders in place of ash to boost the flavor profiles of a variety of dishes. For example, he uses dehydrated corn, lime and red chiles to enhance the flavors in a late summer crab dish.

"If we had a charcoal or wood burning grill, I would play around with it more," Hauck admits. "At Mason Street Grill I used corn husks, leek tops, and onions and grilled them until thoroughly charred then dried them out in the oven. The ash had an earthiness that is hard to explain, not as bitter as you would assume. It was a great supporting element."

Umami Moto's Executive Chef Justin Carlisle has been working with vegetable ash for upwards of 10 years. Initially, he used it primarily as an element for preserving. He points to black cod, cured with sugar, salt, orange peel and citrus ash, where the ash not only imparted subtle balancing notes to the delicate fish, but also offered a beautiful contrast in color for the pure white flesh of the fish.

"In the past, ash was used more as a preservative," he says, "but it's moving into a phase of being used more widely as a seasoning. People are intrigued and almost always surprised when we show them everything that a bit of ash can do. They expect it to taste like carbon, but the ash retains a remarkable amount of the vegetables' original character. The secret is in low, slow roasting that captures the essence of the vegetable and concentrates the flavor."

Carlisle is currently using a leek ash as an addition to Umami Moto's lobster roll, which is topped with masago mayonnaise and embellished with leek ash. In this case, the ash adds a slight onion flavor with a bitter note that acts as a foil for the sweetness of the lobster. He's also looking into using ash made from carrots, herbs and hay.

But it was the end of summer salad using eggplant ash that really caught my attention. For this particular ash, he grills seasoned eggplants until they're nearly black and then bakes them in the oven until they're completely dehydrated. He then infuses the ash with grapeseed oil, which gives it a rich, savory, almost creamy quality.

I sat with Carlisle as he pulled together a sample of the salad made from house-cured pig's head bacon, fresh Indigo cherry tomatoes, pickled Sungold tomatoes, scallions, sunflower sprouts, lemon oil, arugula and shiso microgreens. As he arranged the salad on the plate, he spooned eggplant ash on top.

Biting into the salad, a cacophony of flavors – from sweet to briny, bright to slightly acidic – greeted my palate. The earthy, grapeseed-oil infused eggplant ash retained a remarkable amount of eggplant flavor, while providing a smooth, almost silky, texture to the dish.

"I'm not a big grilling fan," Carlisle admits. "The flavor of the char on the exterior of the meat tends to overpower lighter flavors. On the other hand, using the ash pulls those smoky flavors in, without overwhelming the other elements of the dish."

Different? Absolutely.

Surprising? Most assuredly.

But, regardless of what you label them, techniques like creating and using vegetable ash are just the sort of thing that separates the cooks among us from the chefs.