Heat the oil in a large saucepan. Add the bacon and cook for 5 minutes, over a medium heat, stirring from time to time until the bacon is crispy.
Add the onion and garlic and cook until the onion begins to soften, about 5 minutes. Then add the mushrooms and thyme and cook for 1 minute. Stir in the stock and bring to the boil. Add in the pasta and cook for 8-10 minutes or until the pasta is cooked. Stir frequently. Stir through the cheese and allow to cook for another couple of minutes. The cheese will help to thicken the sauce. Taste and season. Just before serving add in the courgettes.