A few years ago, I worked in one of those super-snooty, super-high-end, restaurants. We charged insane prices for great food, we upheld every pretense and reality of the three pillars of fine dining (Luxe, Calme et Volupté) and even the toilet attendants spoke with a faux British accent.
One day, the dining room was a little slow that time, chef looked outside through the window. And he watched a woman lick her plate, right there, in the middle of the room, much to the amusement and dismay of the diners on her table and surrounding ones. He waved the maitre d' over, and I half feared this was our first ejection. "Go over there," he said, "and when they want to pay, tell them it's on me. Also bring them this," and he handed the maitre a full plate of exquisite smaller samples and amuse.
"The cost of this sauce was easily $20," chef explained. "She ate what she paid for. Or, since we're comping her, what she would have. She showed me and you that she loved our food and wanted to eat it. And that my and your work was more important to her than what others thought of her. And that, my friends, is what being a cook or chef is all about. She just validated every single one of us."
So I say, with conviction, LICK! - because there is no reason not to.
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