Heat half the oil in a wide casserole or frying pan. (You can also cook this in a large saucepan, but you may need to break the spaghetti in half to make it fit later.)
Fry the sliced bacon over a medium heat for 1½–2 minutes, or until lightly browned, stirring occasionally. Add the remaining oil, garlic and chilli, if using, and cook for a few seconds, stirring constantly.
Add the stock and bring to the boil. Add the pasta and stir well. Simmer for 10 minutes, stirring occasionally.
When the pasta is tender, but there is still plenty of liquid in the pan, add the tomatoes and spinach leaves. Cook for 4–5 minutes, or until the tomatoes are soft, but holding their shape and nearly all the liquid has been absorbed.
Stir in the grated parmesan, season with black pepper and serve.
