Discard the green stalks and the lower extremity of the fennels, then finely slice them. Peel and roughly chop the potatoe.
Heat 2 tablespoons of oil in a large skillet and fry smashed garlic for a few minutes, stirring occasionally with a wooden spoon.
Pour into the sliced fennels and the chopped potatoe, season with salt, turmeric and black pepper and fry for 5 minutes to let them flavor.
Pour into the broth o water, then bring to the boil and simmer over a low heat for 20 minutes until very soft.
Meanwhile, fry the pancetta in a non-stick frying pan without oil, turning them on both sides.
Cut in stripes and put aside. In the same pan toast some sesame seeds, stirring continuously.
To make the croutons: cut 4 slices of bread into small squares. Heat 2 tablespoon olive oil in a frying pan, then fry the bread until it starts to become crisp.
Blend with a hand blender, then pour into soup bowls.
Garnish with pancetta, sesame seeds, fennel leaves or toasted cut bread.
Serve immediately.