Grilling With Vinegar: Michigan's Olive-Topped Burgers Get a Japanese Twist

Every summer I go Up North. For those in the know, that's northern Michigan, not the Upper Peninsula where the yoopers reside. My wife's family has a little cottage on Bear Lake, 45 minutes south of Traverse City and about 10 miles from Lake Michigan. A handful of years back, we built a wood-fired oven in the backyard and there's a grill on the front deck and a constant supply of cold drinks close by. In between cooking and eating (which takes up the majority of our time there), you'll find me across the two-lane country road in the fresh lake water.

Out-of-towners who take part in northern Michigan's vacation culture are euphemistically called "fudgies," a nod to the group's large consumption of locally made fudge. Some of the most superlative ice creams in the country dot the 45th parallel (Moomers!), and Leelanau County serves the finest fried perch in practically every restaurant. Most other culinary specialties are cherry-centric, yet there is one outstanding anomaly: the olive burger. Briny green olives are bound in mayonnaise and the mixture is dolloped on top of a hockey puck–size burger that's been cooked to medium and smothered in Swiss cheese. I don't know where it came from, but I'd like to imagine that it was borne of the state's obsession with Greek diners. Whatever the case, I'm amazed to find it on nearly all casual restaurant menus Up North—and even if it's not there, most places are happy to make one by special order.

These strangely time-honored olive burgers were the impetus for this even more bizarre mash-up burger, which adds in vinegar from southwest Japan. In Kagoshima, on the island of Kyushu, there are a couple culinary peculiarities: more shochu is imbibed there than sake, and the omnipresent kurozu (black vinegar) is widely regarded as more of a beverage than a pantry ingredient.

Kurozu is made in tsubo, three-foot-tall, dark ceramic jars, from a combination of nothing more than three things: rice, water, and koji (the mold aspergillus oryzae, which is also used to make soy sauce and miso, among other things). The jars are covered and left to ferment in the sun for years, with little more than a sporadic stir with a stick. The final product is similar to Chinese chinkiang vinegar (black vinegar), though less soupy and smoother, like a well-aged whiskey (if all the alcohol burned off and turned into acetic acid, that is). Kurozu, full of antioxidant-rich polyphenols, is often said to have restorative health properties. It's even sold as a sports drink for cyclists. In Kagoshima kitchens it's usually used in dishes from the Chinese cuisine canon—think sweet-and-sour soups, sweet-and-sour pork, sweet-and-sour noodles—which might be expected due to its similarity to chinkiang.

The hardest thing about kurozu is finding it. Well-stocked Japanese grocers may sometimes have it, or you can seek out an online supplier (at the time of publication, this website was selling it). If you can't find kurozu, chinkiang is probably your best bet as a substitute.

After spending a few days in Kagoshima, I brought a bottle of kurozu back to Brooklyn, and I thought for a long time about how to use it in my cooking. Its funk is a bit like that of dry-aged beef, which got me thinking about using it to marinate ground meat. Turns out the match is perfect, with the meat quickly soaking up and blending with kurozu's distinct flavor.

I've since found that if you let the meat marinate in kurozu for much longer than an hour, the proteins tend to break down and the meat becomes a little gummy, so only use it as a quick marinade.

For this burger recipe, I mixed the kurozu with ground beef before forming it into patties. That breaks one of the cardinal rules of burger-making: don't overwork the meat and don't add mix-ins. The secret is to add the vinegar and mix it gently and briefly, just enough to disperse it. Done with care, you won't end up with a tight puck of meatloaf-like meat. And what you gain is well worth it: The kurozu adds moisture to the burger blend, imparting a savory bass note and very slight tang, which is perfect since the burger is otherwise only seasoned with salt.

For the remaining components of this twist on an olive burger, I wound up using oil-cured black olives rather than green ones. Their salty, umami, and floral qualities match the darkness of the kurozu-flavored meat so nicely.

Grilled on high heat for a few minutes per side, topped with melted cheese, and then placed on a grilled brioche bun, a spoonful of olive-studded mayo is the crowning glory to one big multicultural bite.