No, that creamy white beverage placed in front of you at your favorite Mexican spot is not milk for your coffee — and no, it’s not RumChata, either. This mystery milky beverage is pulque, one of Mexico’s most historic drinks. Its sour, yeasty flavors have become super popular nowadays among mezcal and tequila lovers alike. So what the hell is it?

Pulque (pronounced pull-kay) is an alcoholic beverage based on the fermented sap of the maguey plant. The drink has been made in central Mexico for thousands of years, dating back to the Mesoamerican period. After a brief fall in popularity in the 20th century — thanks to the rising popularity of cerveza consumption among Europeans — pulque is back on the market and, from what it looks like, here to stay.

There’s quite a bit of mythology surrounding pulque; after thousands of years of consumption, you can understand how some stories have spread. One of the more popular myths is that the maguey plant’s center was filled with the blood of Mayahuel, the goddess of the plant. Another legend has it that Tlacuache, another mythical character, extracted pulque juice with his bare hands, which led him to be the first drunk.

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Pulque’s popularity is strongest in central Mexico because this is where the maguey plant thrives; the cool, rocky climate is actually beneficial to the plant’s growth. Believe it or not, it takes a solid 12 years of maturity for a maguey plant to create enough sap for pulque production! But the stuff is worth the wait.

Pulque is a creamy, whiteish-colored beverage with a slight foam. The drink comes from the fermented (not distilled) sap of one or more of six specific varieties of the maguey plant. Pulque is drunk all over Mexico, in bars called pulquerias. Many pulquerias hold a tradition of leaving sawdust on the floor, for the sole purpose of offering up little spills of pulque to the Earth. When a fresh delivery of pulque has been made to a pulqueria, the owner of the joint will generally hang a white flag over the door. Pulque is usually poured into glasses from large barrels that are on ice.

As if the enticing history and traditions aren’t enough to convince you to try it, many have noted the health benefits of drinking pulque, including amino acids, vitamins C, D, and E, and iron. We’ll drink to that.