Celery soup with blue cheese

30 gr of butter, 1 head of celery, 2 onions, 2 spoons of flour, 1.2 litre of vegetable broth, 75 gr blue of cheese (spicy Gorgonzola, Stilton, Roquefort), black pepper, chives, salt

Peel, wash and cut into small cubes the celery and the onions. In a wide pan melt the butter, add the celery and onions and cook for about 4 minutes. When the onions are translucent, add the flour and cook for another minute. Pour the broth little by little and mix well, let it simmer for 30 minutes, until the celery is soft. Crumble the cheese, add it to the soup, season it with salt and pepper, put in in the blender and mix well. Serve sprinkled with chives and eat it with croutons.