See the recipe: Board Sauce Recipe
Here’s how the concept works. He takes a handful of fresh herbs and chops them on a cutting board. Then he pours some olive oil on the herbs, minces them together, lays hot grilled meat on the mixture, carves the meat, and tosses the cut meat in with the board sauce, which is enriched by the meat juices. The board sauce keeps the meat moist, and brings interesting flavors to the insides of the meat. Surprisingly, shockingly, the herbs do not overpower the meat. I’m one of those guys who uses only salt and pepper on my steaks because they are so wonderful when cooked properly and I don’t want to mask them. But board sauces do not mask the meat.
APL recommends 6 tablespoons of oil to 2 tablespoons of fresh herbs such as thyme, rosemary, sage, and parsley, but I’ve used oregano, basil, mint, garlic, black garlic, and others work fine depending on the meat and your tastes. And you don’t have to measure. Lang occasionally uses rendered fat from the meat instead of olive oil, and sometimes adds balsamic vinegar, wine vinegar, citrus juices, lemon zest, fresh garlic, shallots, chiles, and scallions. If you wish you can add salt and pepper but be careful that you don’t overdose if salt is already on the meat.
I often chop the herbs while the meat is cooking and put them in a coffee cup. Then I pour in enough oil to cover them so the oil has a chance to extract more flavor from the herbs. But you cannot make it up hours in advance because the anaerobic (oxygen free) environment in the oil is friendly to the botulism microbe. Even in the fridge. If you make it in a cup you can serve a whole steak to each guest and just spoon some sauce on top