Broccoli & stilton soup

INGREDIENTS

• 2 tbsp rapeseed oil
• 1 onion , finely chopped
• 1 stick celery , sliced
• 1 leek , sliced
• 1 medium potato , diced
• 1 knob butter
• 1l low salt or homemade chicken or vegetable stock
• 1 head broccoli , roughly chopped
• 140g Stilton , or other blue cheese, crumbled