Rock Tripe is a common group of lichens (Umbilicaria spp or Gyrophora spp) found on the rock outcrops and cliffs around Mantario. The lichen looks like a large leathery leaf or dry leather attached by the centre to the rock. It may be brown or gray and usually has a black velvety back. When dry it is stiff and brittle, after a rain or when the lichen is wet it becomes soft and rubbery.
Many sources report individuals or groups of people surviving on rock tripe as a subsistence or emergency food. Before eating most lichens they should be treated to remove or neutralize the bitter acids which can cause stomach and bowel complaints and nausea - even when treated some lichens should not be eaten. Treat the rock tripe by soaking the collected material in water with a teaspoon of baking soda for each liter of water. Simmer the rock tripe for 30 min with at least one change of water. The material should be rinsed with clear water when finished.
Bring the water to a boil and simmer above ingredients for 10-15 minutes.
Mix cornstarch in a little water and stir into the soup. Add the oil and vinegar and simmer for a few minutes. Beat the egg and stir into the soup. Cook for another couple of minutes.