Heat oil in a large saucepan over medium heat. Add onion and garlic and cook, stirring often, for 3 minutes. Add celery and potatoes and cook, stirring often, for 5 minutes.

Add stock, cover and bring to the boil. Reduce heat and simmer for 25 to 30 minutes until tender. Set aside to cool slightly.

Puree soup until smooth. In batches, push mixture through a fine sieve over a large bowl and discard stringy pieces in sieve. Return soup to pan.

Stir in cream and heat over medium heat until hot (do not boil). Crumble 50 g blue cheese into soup and season with salt and pepper. Stir until cheese melts. Ladle into serving bowls and serve with remaining crumbled blue cheese and thick wholegrain toast.