Why this pairing exists
Mole is not a sauce. Mole is a category. There are dozens of varieties, from the deep brown mole negro of Oaxaca to the red mole coloradito to the green mole verde. They are all built the same way: chiles, nuts, seeds, spices, sometimes chocolate, sometimes fruit, ground together into something that takes hours or days to make and tastes like a civilization.
Mezcal is the same thing, but in a glass. Chiles, earth, smoke, time. Both come from Oaxaca, or near it. Both are older than the Spanish. Both are made by people who have been doing it the same way for centuries.
When you put them together, you are not inventing a pairing. You are recognizing one that has been there all along.
The rule
Match smoke with smoke. Match earth with earth. Match the intensity of the mole with the intensity of the mezcal.
A light mole verde — green, herbal, made with tomatillo and pumpkin seed — wants a light mezcal. Something from the Espadín agave, unaged, bright, with less smoke.
A heavy mole negro — dark, bitter, made with chocolate and burnt chiles — wants a heavier mezcal. Something aged in oak, or a wild agave like Tobalá or Madrecuixe, with more smoke and more body.
If you pour a heavy mezcal with a light mole, the mole disappears. If you pour a light mezcal with a heavy mole, the mezcal disappears. Same rule as whiskey and chocolate. Same rule as everything.
The serving
Mezcal is served at room temperature, in a small clay cup or a veladora. Not in a shot glass. Not chilled. Not with salt and lime unless the mezcal is rough and you need something to hide behind.
Mole is served hot. Not warm. Hot. The heat is part of the dish. The mezcal is cool by comparison, and the difference is the point.
Take a bite of mole. Let it sit for a second. Take a sip of mezcal. Let the smoke meet the chile. That is the whole ritual, and it does not need to be more complicated than that.
What to avoid
Do not put mezcal in the mole. This is a thing people do, and it is not wrong, but it is a different dish. The mole already has mezcal in it in some kitchens. If you add more, you are not pairing. You are repeating.
Do not drink the mezcal as a shot before the mole. The shot is a tourist move. Sip it. Let it be part of the meal.
Do not skip the tortillas. The tortilla is the vehicle. Without it, the mole is too intense to eat more than three bites of. With it, the mole can go on for an hour.
So what
Mezcal and mole is not a pairing you have to learn. It is a pairing you have to stop avoiding. It is a part of the culture it comes from. If you are in Oaxaca and you order mole and you do not order mezcal, you are doing half the thing.
Order both. Sit down. Eat slowly. Sip slowly. Do not take a photo of the plate. Eat the plate.