Not to be confused with Pachamama (mother earth for the Incas), Pachamanca is the equivalent to the American barbecue. Just like you might have a cookout or barbecue to celebrate a special event with friends or family, making Pachamanca is the classic way to celebrate an occasion with family and friends in many parts of Peru.
Two of my going-away parties were celebrated with Pachamanca. My host family prepared Pachamanca for a family wedding. The town of Quillazu celebrated its anniversary with Pachamanca. We celebrated the renovation of the water system in a community called Los Angeles with Pachamanca.We celebrated my friend (and the local tree expert), Alfonso’s birthday with Pachamanca. You get the idea.
Pachamanca is a typical plate originating in the Sierra (highlands) of Peru but common in most parts of the country. Even in Lima, during my first month of training I had already been introduced to Pachamanca. I couldn’t believe that so much food could fit on one plate and I couldn’t believe they expected me to eat it ALL! By my second year in service, I was serving my own heaping plate of Pachamanca and eating it all (for better or for worse)!
So what is Pachamanca? There are variations on the theme, depending on where you are, but in short, it is meat and tubers marinated in herbs and cooked in an earthen oven, often with a type of bean called “habas”. Depending on where you are the meat could be sheep or pork or chicken. Sometimes it can also include corn or plantains.
But Pachamanca is not just the food – it has a special element of the community activity of preparing it. (In the fast-paced world of today, sometimes a “pachamancero” can be hired to prepare it, and sometime it’s prepared in an oven.) But traditionally, and more commonly, it’s a community activity of preparing it, and the preparation is part of the celebration.
To be clear, I am not an authority on Pachamanca, (a real pachamancero has an expert technique for the whole process), but so that you get the idea, here’s the process I saw in Oxapampa:
First, the marinade is prepared from local herbs and the meat and tubers are marinated overnight – usually pork or chicken and potatoes (papas), yucca (yuca), sweet potatoes (camote), and sometimes my favorite tuber, pituca.
To cook Pachamanca, you start a fire and put large stones in the fire to heat up, while you dig a hole in the ground. Often the hole is lined with banana leaves. Then the hot rocks are placed in the hole. This is your oven. 
The tubers (potatoes, yuca, sweet potatoes, and sometimes pituca) are added in the first layer with the hot rocks.
Often separated by banana leaves, a second layer of meat and hot rocks is created.
Then another layer separated by banana leaves contains habas (a type of legume).
Everything is then covered with banana leaves before the hole is covered up so the oven can cook.
For about an hour or so, everyone hangs out, chatting and enjoying each other’s company (often enjoying a cerveza) while the pachamanca cooks.
About about an hour or two, the oven is opened, banana leaves peeled back, and the Pachamanca emerges – deliciously roasted meat, potatoes, sweet potatoes, yucca, plátano, and habas.
The food is carefully collected from the earthen oven.
And finally it is all arranged mountainously on each plate.
Buen provecho!