Why do I begin a food focus with a recipe for making your own chorizo? After all, there's no shortage of places to buy it at a reasonable price. Apart from allowing you to choose the amount of spiciness that suits you, though, it has much to teach us about the history of 'typical' Spanish food.
Spain until the death of Franco in 1975 was a country with an economic chasm between rich and poor. Especially in the south there was the system referred to as 'latifundia', which is to say that the rich - mainly absentee - landowners possessed vast estates relying on day labourers to do the work. The work such as it was, was was seasonal, casual and poorly paid. Families lived in cramped properties on a small plot of land which had to supply everything they needed. Maybe a few olive trees, a vegetable garden providing potatoes, onions, garlic, root vegetables, maybe tomatoes, peppers and beans - eaten green in the summer or dried for eating over the winter. Meat was either by chicken or by a pig. The chickens also provided eggs, but the most important meat was pork, and every family had its pig, bought young in the spring, fattened by whatever it found and by kitchen scraps. Then in November came La Matanza, the slaughter. The animal was slaughtered at home and the hard work began; the throat was slit and the blood drained into a large cooking pot where it was mixed with some form of cereal and then boiled to be spiced and packed into gut and made into black pudding to be dried and eaten through the winter. The loin was for early eating while still fresh. The belly provided bacon. The hind quarters were packed in salt, then hung in a cold, dry atmosphere to produce what we now refer to as Serrano ham. Just about every part was preserved so that it could be used as necessary right through the winter.
That then left the bits and pieces which couldn't be used in any of these ways. Some could go into stews with vegetables and pulses to be eaten pretty much straight away. Then there were the remains bits. They were ground down along with garlic, smoked paprika, maybe chilli, and packed into intestines. And there you have chorizo!
In Britain sausage is sausage; you can eat it with mashed potato, with a batter for toad in the hole, or with flaky pastry as sausage rolls, and that's about it.
Chorizo, on the other hand can be used in a huge variety of stews and casseroles - peppers, tomatoes, potatoes, chickpeas; it is not so much a product in its own right so much as a preserved ingredient providing a source of protein in the winter diet. When you live on or below the poverty line such sources of protein are vital to survival; chorizo serves a much wider and more fundamental purpose than today's British banger.