Melt the butter in a large and deep pot over low-medium heat. Add the onions, sprinkle lightly with salt and saute, stirring often, until they become tender and deeply caramelized, about 20-30 minutes. Remove the pot from the heat and add the wine. Return to a low-medium heat and deglaze the pan by scraping up all the brown bits that have accumulated.
Add the apples and garlic and gently stir until the garlic is fragrant, about 30 seconds. Add the broth, cider and potatoes. Add the salt and pepper and stir to mix well. Raise the heat and bring the contents to a boil. Lower the heat and simmer, uncovered, until the potatoes are tender, about 20 minutes, they should easily pierce with a fork.
In the meantime, frizzle the sage leaves by adding the olive oil to a medium skillet with deep sides. When the oil is hot and shimmery, add the sage leaves – careful as they often pop when sizzling. Fry until crisp, 1 minute. Using a slotted spoon, transfer the sage to a paper towel lined plate to cool. They will continue to crisp-up more as they cool down. Don’t discard the sage-infused oil, set it aside to very lightly drizzle onto each serving.
Turn off the heat under the soup mixture.
Using a blender with a heat tolerant canister, slowly ladle the soup in small batches, careful to only halfway fill. Note that overfilling will result in the hot soup popping the lid. Working in small batches, with the lid on, and with a kitchen towel over the lid, blend the soup until it is smooth. The consistency of the soup should be thick and creamy, bisque-like, with fluidity and movement (see notes below). Transfer to a medium-sized pot and keep the soup over low heat. Continue pulsing the rest of the soup in the same way.
Taste and adjust the seasonings, if necessary. Remove the soup from the heat and ladle into individual bowls. Garnish each bowl with a dollop of sour cream and frizzled sage leaves. Drizzle lightly with the sage infused oil, if desired.
Notes
*An easy way to sliver sage leaves is to take a few at a time and gently roll them up, like a scroll. Using sharp kitchen scissors, cut into thin strips. Loosen the strips after they’ve all been cut as some will likely want to stick together.PRO TIPS:Your judgment is as important as the ingredients you use. So, while the consistency of the soup should be somewhat thick and bisque-like:
If the potatoes used are too large, it could result in a soup that is thicker than desired. To thin, warm up extra broth and add it into the soup a little at a time, until the desired consistency is reached. Taste and adjust the seasonings if necessary.
If the apples on hand are quite small, consider using four of them instead of two medium apples as indicated.
If the soup is too thin after blending, consider adding heavy cream in at the end (after the soup has been heated through and is off the heat). Start with 1/4 cup (60 ml) of cream and add it in slowly while whisking, until the desired consistency is reached. Taste and adjust the seasonings if necessary.
This soup pairs beautifully alongside roasted chicken, as a first course before holiday turkey, or paired with a pork dish and a crisp autumn salad with chopped apples.Other garnish to consider: thinly sliced apples, roughly chopped crispy bacon, homemade croutons.