Prepare the products. I have half a serving here, my husband and I are together, and there was a lot of it. Wash and peel the vegetables.
Finely chop the onion. Cut off the feathery tops of the fennel and leave to decorate the soup. Cut the bulbs into 4 pieces. Cut one quarter very finely and put it in a bowl with lemon juice, mix well. Cut the rest of the fennel into arbitrary pieces.
Peel and slice the mushrooms, and cut the potatoes into small cubes.
Pour the vegetable oil into a large saucepan. Add the onion and simmer lightly.
Add the fennel, stir, cover and cook over medium heat for 5 minutes, shaking the pan periodically. Vegetables should be softer, but not toasted.
Add the potatoes.
And mix the mushrooms well, pour in the sherry and broth.
Bring to a boil, reduce the heat, cover and cook for 30 minutes until the potatoes are boiled.
Whisk the soup into a puree using a blender. Return to the pan.
Add salt, black pepper and lemon zest.
Add cream or milk, warm up if necessary.
Grate the cheese on a coarse grater. Mix the remaining finely chopped fennel with grated cheese.
To make the dish really satisfying, spread a mixture of cheese and fennel on thick slices of bread and fry until golden brown.