Heat two tablespoons of the oil in a frying pan over a medium heat. Add the onion, garlic and celery and fry for 4-5 minutes until softened. Add the broccoli florets and the vegetable stock pot to the pan and pour in 750ml boiling water. Bring the liquid to the boil, then reduce the heat and continue to simmer for 12-15 minutes, or until the broccoli florets are tender. When the soup has simmered, blend it until smooth using a stick blender. Add the cream and Stilton and blend again until smooth and well combined. Season, to taste with salt and freshly ground black pepper. In a small frying pan, cook the pancetta for 3-4 minutes until brown and crispy. To serve, spoon the soup into bowl then sprinkle over the crispy pancetta and chopped parsley.