20g butter, or rapeseed or sunflower oil
1 large or 2 medium onions, diced
1 bay leaf
About 200g potato peelings (about as much as you’d get from preparing a decent-sized tray of roast potatoes)
500ml whole milk
500ml chicken or vegetable stock
2 tbsp finely chopped parsley leaves (optional)
Salt and freshly ground black pepper
Fried sage leaves
Crisp-grilled bacon (optional)
Heat the butter or oil in a medium saucepan over a medium-low heat and add the onions, bay leaf and a good pinch of salt. Sauté gently, until the onions are soft but haven’t taken on much colour, about 10 minutes.
Add the potato peelings and give everything a very good stir for a minute.
Pour in the milk and stock, season well with salt and pepper and bring to the boil. Reduce the heat and simmer gently until the peels are very tender – another 10 minutes or so.
Remove from the heat and cool slightly, then purée in a food processer, blender or using a stick blender until very smooth.
Return the soup to the pan and reheat gently. Season well with salt and pepper and stir in the chopped parsley, if using.
Serve in warmed bowls, topped with fried sage leaves and shards of crisp-grilled bacon, if you like. Finish with a generous grind of pepper.