Heat the oil in a saucepan and gently fry the spring onions, celery, garlic and courgette for 10 minutes. Season well and add the stock. Bring to the boil then add the pasta and cook for 10 minutes. Stir through the peas and cook for a minute or two more. Season to taste.
Meanwhile, set your finely chopped broccoli to one side. Mix the two cheeses together. Heat an ovenproof frying pan or griddle over a high heat. Butter both the inside and outside of your bread slices and spread the inside with dijon. Layer up 4 of the slices with cheese, broccoli and then a little cheese again. Top with a second slice