Chocolate para mesa_, unconched chocolate.
Chocolate as we know it has only existed for a few hundred years. Modern chocolate is "conched" by grinding it for up to 72 hours to give it a smoother texture. Before the Europeans perfected the process of refining chocolate, the cacao bean was used to make a beverage for over 3000 years in Central America.
Mexican chocolate is closer to what chocolate probably tasted like prior to the development of the conching process. It's very gritty with a crumbly texture that reveals granules of sugar. A look at the ingredients of Ibarra, the most common brand of Mexican chocolate, reveals that there are only 4 ingredients: sugar, cacao nibs, cinnamon and an emulsifier.
What's it taste like?
It's typically not eaten straight because of the texture but when mixed with hot water or milk, it makes a fantastic beverage. It's nutty and sweet with a faint spiciness coming from the cinnamon.
Where do I get it?
Grocery stores in North America that have a Latin American food section should carry it. Otherwise go to a Latin American specialty food store. Ibarra, the most common brand comes in a yellow and red hexagon shaped box with individually wrapped wheels of chocolate inside.
When is it best?
There's no season, but it can go rancid if it's too old. Try to buy it from a store that looks like they go through a lot of it.
How do I use it?
The most common use is for making Mexican hot chocolate by mixing a few wedges of a wheel with a cup of hot water or milk. You can add extra cinnamon or some cayenne pepper for some extra kick. Mixed with Masa Harina and cooked with water it makes a thick porridge-like beverage called atole de chocolate. It's also added to mole to add sweetness, body and a nutty flavour to the sauce.
It contains a lot of sugar, but the cacao in it is high in iron, calcium, magnesium, potassium, and anti-oxidants.