This soup has a surprising subtle tangy taste you will surely like.
Select sauté at "medium or normal", put 15 minutes and start cooking as soon as the inner pot is hot. Melt the butter and cook the onions, celery and leeks for 5 minutes, stirring constantly with a wooden spoon. Add the potatoes and apples and cook 2 minutes. Press "cancel".
Add broth, cinnamon and nutmet. Secure lid with press release button at "sealing".
Select « soup, pressure cook or manual », put 12 minutes at « high » with «keep warm at off ». Press « start ». (It will take about 10 minutes to build pressure and begin cooking).
When the end of cooking alarm sounds, wait 10 minutes before releasing pressure.
Purée soup with an immersion blender or a blender. Filter through a sieve for a finer texture.
Season with salt and pepper.
Place 2 thin slices of apple and a dash of nutmeg on each serving.