Heat a bit of oil in a large pan and add the onion, garlic, celery and carrots. Season to taste and cook till softened and golden brown.
Add the mushrooms and cook, stirring constantly, till the mushrooms are soft. Add water and chicken stock pots, and bring to the boil. Once boiling, add the milk and bring to the boil again.
Add the spinach and stir through. Cook till wilted and the soup is warmed through.
Crumble in as much Stilton as you'd like. Taste and adjust the seasonings, then blend the soup till smooth. Enjoy.