This soup is born out of a restaurant disappointment. It was a fancy restaurant, too, one of those places in the US where they charge over $10 for a bowl of what is basically a potage (blended vegetable soup). There was something called a “foie gras” dumpling on top, which made the dish sound like chef had come up with a late autumn masterpiece worthy of foie gras.
Alas, what came to the table was a far cry from the rich, thick, earthy bisque I was craving. Instead, a thin, weak, undersalted liquid had been sloshed into a shallow bowl and topped with a fast-sinking cube of…something. The foie gras dumpling, I guessed. The soup had a faint orange hue (the squash) and an even fainter hint of chestnut flavor. It wasn’t even hot enough. (I had to send it back to the kitchen where, from what I can tell, the chef just nuked it.) With each spoonful, I yearned for a better version. I vowed to make a better version.
So, the moment I got to a grocery store back in France, I reached into my stash of pre-cooked chestnuts and put together “my” take on a winter squash and chestnut soup.
There’s nothing to it, really—though I did add a cognac deglazing flourish for flavor and for fun. It’s your basic blended vegetable soup…only the chestnuts take it waaaay on over to the next level with their sweet, creamy, nutty, earthy, and oh-so-satisfying flavor. So I’ve called it a bisque. It would probably go well with foie gras, but it tastes rich and decadent enough on its own…and I didn’t add any cream. (You could, though.)
My “finishing touch” was a Breton twist and a swirl of buttermilk rather than cream or crème fraiche. Call it an homage to bygone days (and I still have neighbors who remember those days), when poorer folk in Brittany used to pour buttermilk over hot roasted chestnuts and make that their evening meal.
2 Tbs. butter or olive oil
2 leeks, white parts only, finely chopped (1 cup)
¼ cup cognac, optional
4 cups (1 lb./500 g.) red kuri squash cubes
1 cup (1/2 lb./250 g.) peeled cooked chestnuts, plus more for garnish
sprig fresh thyme
sprig fresh sage
buttermilk, optional (you could also use yogurt or sour cream)
Heat the butter or olive oil in a large saucepan over medium heat. Add the leeks and a pinch of salt, and sauté 5 to 7 minutes, or until the leeks are softened. Pour in the cognac, if using, and simmer until all the liquid has evaporated. Add the squash, chestnuts, thyme, sage, and 4 cups water, and season with salt and pepper. Cover, and bring to a boil. Reduce the heat to medium-low, and simmer 30 minutes, or until the squash and chestnuts are very soft.
Remove the herbs, and blend the soup with a hand-held immersion blender or in a stand-up blender until smooth. Adjust the seasonings. Serve hot with a chestnut crumbled on top of each serving and a swirl of buttermilk, if desired.