Back in 2008, renowned Danish chef René Redzepi and restaurateur Claus Meyer, now known to foodies as the masterminds behind the four-time world’s best restaurant Noma, opened a peculiar test kitchen in Copenhagen. The Nordic Food Lab, as they called it, was a space for chefs to experiment with the weird, new, and taboo in a way they never could in a working kitchen. Ever since, they’ve scored headlines with reports on cooking with fermented grasshoppers, pheasant essence, and even beaver anal glands. But perhaps no report they’ve issued has garnered as much attention and consternation as the one released this January by then-Food Lab intern Elisabeth Paul on how to substitute blood for eggs.

Blood-based cooking has certainly been a part of Western cuisine since the time of ancient Greece, when blood sausages were mentioned in Homer’s Odyssey. And in all likelihood, people have used animal blood for sausages, soups, pastes, or drinks since the first animal slaughter. But sometime in recent history, we forgot how to use blood. The ingredient grew so taboo that even Scottish chef Nick Nairn vomited on television at the site of a bowl of cooking blood.