Read the passage and answer the questions.

Sausages have been a popular food for thousands of years. They are made from a mixture of ground meat, fat, salt and spices. Traditionally, certain cuts and parts of animals that would not be served in their original forms are used to make sausages, so that no part is wasted. Although many kinds of meat can be used, beef and pork are by far the favourite meats for making sausages. Once the meat mixture is prepared, it is placed inside a cleaned intestine, which acts as a natural casing. Sausages can be cooked in several ways, such as grilling, frying or baking, but boiling is the simplest method.

What is the simplest method of cooking sausages?