Place the spaghetti in a large pan of boiling salted water and cook according to the package instructions.
Whilst the pasta is cooking open the anchovies and pour them into a large frying pan, cook over a low heat stirring all the time, until the anchovies "melt" and make a sauce.
Add the garlic, chilli, and the capers, sun dried tomatoes and olives (if using). Cook for a few minutes.
Once the pasta is cooked reserve a cup of cooking water and add a splash to the anchovy mixture.
Drain the pasta and give it a good shake. Add the the frying pan and stir well so it is coated with the anchovy sauce.
Stir through the avocado (if using), Parmesan and chopped parsley and serve immediately.
Easy Chilli Anchovy Pasta - Hints & Tips