I went to find the recipe I used, and realised how much I'd deviated from it. But it was good, very good, and so I'm writing it down before I forget it.
Melt one tablespoon of butter in a large pot. Dice a large white onion and fry gently until soft.
Meanwhile, take one head of garlic and slice the top off, leaving most of the garlic intact. Mince the clove tips you've just sliced off, and add to the onions after five minutes. Fry for another minute whilst boiling kettle.
Pour in about 1.5l stock (boiling water and bouillon cube if you're me), toss in the head of garlic (whole), and simmer until the garlic is soft.
Add the inside of one courgette, having used the skin to make ribbons for a veggie pizza which you will later forget to offer to your guests. Oops.
As the stock simmers, peel the potatoes (around 2lbs) quite thickly, saving the skins. Dice the insides.
When the garlic is soft, remove from stock, squish, discard skin and roots and put the pulp back in. Add the diced potatoes and simmer until potatoes are soft.
Turn oven to 220c. Put potato skins in baking dish, toss with oil, salt and fresh chopped rosemary to taste. Roast until crispy.
Mash or purée the potato soup, taking care not to over blitz if using a blender to avoid turning soup into glue.
Turn off, worry that stock was too salty. Leave to consolidate flavour for two hours whilst drinking coffee with friends. This step may be omitted.
Bring soup back to heat and stir in sour cream (a couple of heaped tablespoons maybe?).
Serve in bowls, adding potato skins in place of croutons.