You'll need to soak your fava beans overnight, up to 12 hours. (Dried fava beans are quite a bit harder than other beans and need longer soaking.)
Put your favas in a pot large enough to contain them and enough water to cover by a couple of centimeters (about an inch). Season well with salt and pepper, along with the optional ingredients if using
Simmer about an hour or more, until the favas have become very tender. Stir frequently and top up with more water as needed to prevent the beans from drying out and scorching, but you do want to water to reduce, so that by the time the favas are tender, the water will mostly have evaporated.
When the beans are tender, begin to mash them with the side of your wooden spoon, until the beans have formed a kind of 'cream'. If you want a smoother texture, use an immersion blender or pass the favas through a food mill and return them to the pot. Add a good pour of olive oil to enrich the beans. Continue simmering, stirring all the time, until the beans have formed a purée thick enough that you can form a little 'canal' with a wooden spoon as you stir. The purée should have the texture of mashed potatoes.
Taste and, if necessary, adjust for seasoning.