Okay, step one?you have to add some butter to a pan but don’t let it go brown at this point. Now julienne the onions. When you do a julienne you should always slice from top to bottom. This means you’re slicing with the grain and it will help the onions retain their shape as they get cooked down.
You now add the onions to the pan, toss them around so they get coated with the melted butter. Keep the heat fairly low. This will help the onions get perfectly sweet and brown all over as opposed to merely caramelising the edges. Add a little salt. This will not only season the onions, but will shorten the whole process. In theory, salt will raise the temperature of the onions and help them cook faster.
You should be able to see that the onions are about halfway there. Keep stirring them so they don’t stick to the pan and so they all get caramelised evenly. After a little more stirring you should now have caramelised onions. They can be used in numerous ways; pasta, on a pizza spread or a carpaccio, a hamburger, sandwiches and the list goes on.