I have felt chilled to the bone all day and tonight just wanted to feel warm and comforted from the inside out. As well, cleaning out my fridge has been on my to-do list. This soup fit the bill in every way and quite honestly was one of the best things I've eaten in a long while. Mmm!
I recognize that roasting the chestnuts requires a baking sheet which might ruin the one-pot'ness but the chestnuts are optional. —em-i-lis
head of garlic, roasted until tender
fresh chestnuts, each scored with a paring knife around its perimeter, OPTIONAL
Preheat the oven to 400°.
If you've not already...On a piece of foil, put the unpeeled garlic cloves, drizzle with a bit of oil, seal tightly and roast in the oven for 20 - 30 minutes.
If you want to use the chestnuts, place them on a rimmed baking sheet and roast for 30 minutes.
In the meantime, in a dutch oven or soup pot, heat the butter and olive oil over medium-high heat. When the butter is mostly melted and things are heating up, add the chopped leeks, onions, shallots and thyme sprigs. Sprinkle with the salt, nutmeg and white pepper, stir to combine everything well, and lower the heat to medium.
When the veggies are nicely wilted and starting to turn translucent (at least 10 mins), add the sunchokes and chicken broth (and the bacon if using). Turn the heat up to medium high, and submerge the two cheese rinds. After a few minutes, add the buttermilk and cream and stir again to combine everything well. Bring to a boil, then reduce heat until you can maintain a nice simmer and cook 25-30 minutes, until the sunchokes are easily pierced with a knife. Add the roasted garlic cloves (peeled of course) at any point before the cook time is up.
When the sunchokes can be pierced, turn off the heat and carefully remove what's left of the thyme sprigs and cheese rinds. Then, carefully puree the soup with an immersion blender (if you don't have one, let the soup cool some before using a blender).
Serve with peeled and chopped roasted chestnuts and slivered scallions if you like.