Café de olla — coffee of the pot — is simmered with piloncillo and cinnamon in an earthenware olla.
The ingredients
Piloncillo is unrefined whole cane sugar, sold in hard cones. It tastes of molasses and caramel rather than simply sweet, and it is a genuine flavor ingredient rather than a sweetener.
Canela — true Ceylon cinnamon rather than cassia — added as a stick.
Sometimes orange peel, star anise or cloves.
The clay pot
Traditional and not merely decorative: unglazed earthenware contributes a distinct mineral, earthy note that Mexicans describe as essential. A metal pan makes the drink; a clay olla makes café de olla.
Making it
Bring 1 liter (about a quart) of water to a simmer with 60 g (2.1 oz) of piloncillo and a cinnamon stick until the sugar dissolves.
Add 60 g (2.1 oz) of coarsely ground coffee, take it off the heat, cover, and steep for five minutes.
Strain and serve in clay mugs.
The history
It is often said to date to the Mexican Revolution, when it was made for soldiers — sweet, strong and warming, from whatever coffee was available.
Which coffee
A medium-roast Chiapas or Oaxaca, coarsely ground. There is no point using an expensive delicate coffee under this much sugar and spice.
Without piloncillo or a clay pot
Piloncillo is sold in Mexican groceries in the US, often as cones labeled panela. Dark brown sugar with a spoonful of molasses is the closest substitute. A heavy saucepan works if you have no olla; the drink loses its earthy note but keeps its character. Ceylon cinnamon is softer and more floral than the cassia sold as cinnamon in most US supermarkets, so use less cassia if that is what you have.
Serving it
Café de olla is served hot, black and already sweet, in small clay jarritos. It is a morning and evening coffee, and a fixture at holidays.