Butternut squash lends itself well to soup, and it seems that every cook has his or her own version, each with some special twist that makes it better than all the others. For my part, I like my butternut squash soup to taste like butternut squash, without a lot of added cream and butter. The crab makes a nice garnish for the silky soup, which has the crisp, pungent bite of shallot and the coolness of olive oil.
To extract the greatest flavor from the squash, it’s important to cook it in as little water possible. As is true with root vegetables, most of the flavor in butternut squash is water soluble, so the more water you drain away after cooking, the more flavor you lose. The rule of thumb is to use a pot just big enough to fit all the squash and then to add only enough water to barely cover it.
In a soup pot over medium heat, sauté the onion in 1/2 cup of the olive oil until it is soft and beginning to brown, about 5 minutes. Add the squash and just enough water to barely cover it. Season the soup generously with salt, bring to a simmer, and continue to simmer until the squash is soft enough to mash easily with a spoon, about 20 minutes. Drain, then transfer it to a blender (use caution when blending hot liquids) and purée until it is super fine and silky.
For the garnish, mix the crab with the remaining 1 tablespoon olive oil, the shallot, herbs, and orange zest. Toss to combine and season to taste with salt. Divide the garnish among 4 bowls, then ladle in the soup. Serve immediately.
Serves 4 as a first-course soup