Zuppa di Porri - Authentic (guaranteed) Tuscan Leek Soup

This is the simplest most divine soup on the planet and will impress your guests beyond all limits.
This should take about an hour to prepare. Recommendations: use the
best chicken broth available, bone broth (now available in tetrapak) is tops. Use ONLY the white portion of the leeks. You may cut up to where it is yellow at the core but once it becomes more than halfway from the core out, yellow? Stop. Save the rest for a broth or a stew or a roast. Obviously you will cut the dark green leafy portion off and toss.
Ingredients:
6 medium leeks with more than 2 inches of white at the base. If the leeks are smaller and have very little white at the base, use 12.
Parmigiano Reggiano or real Gruyere
50 gm butter
2 generous soup spoons of flour
1.5 liter broth
black pepper
Olive Oil EV First Cold Pressed
Since we do not have Tuscan bread here in the states, use the best French baguette you can find to make the cheese toasts. You may also make bread cubes toasted with olive oil and when hot from the oven, toss with parmigiano reggiano cheese to coat and place back into oven for a brief time to melt the cheese to the bread, set aside. If you do choose to make croutons, use a good country loaf.
If using the French Baguette, slice thin, roast both sides in the oven, either broil or hot, hot oven. Once the second side is toasted, take out and place slices of real Gruyere cheese, place back in oven to melt. When done, remove, cool and set aside.
Method:
Thinly slice the leeks.
Melt butter in 2qt pot. When bubbly, add the leeks.
Saute on medium for 2 min. Add the flour using a sifter or strainer or just rain it in to the mix. You will be making a type of roux but with flour coated leeks. If you think you need a bit more flour, add it without worry. Turn up the heat a bit so you can try to get a toasted roux mix, stirring constantly. When it has a little toasted color, add all your broth at once. Bring to boil, then drop the temp to low. Cover and cook for 25 min. Uncover for the last 5 minutes. If it seems to runny, cook another 5 min or so to evaporate and if it turned out real thin, take some of the broth out in a small bowl, add flour by the teaspoon, stirring so you can add that to the pot without it clumping. Add black pepper and stir. Taste to correct salt if necessary. The leeks should be cooked so well they almost disintegrate making a nice thick but still fluid soup.
Serve in French onion type bowls or nice rustic Tuscan terracotta bowls. Garnish with a drizzle of olive oil, a little parmigiano and the toasts or croutons and any extra pieces of bread, place on the table to add while eating.