Come fall, winter squash are everywhere in farmer's markets and grocery stores, stacked everywhere like an odd assortment of mutant pumpkins. Don't be daunted: pear-shaped butternuts, the best of these vitamin-packed powerhouses, are dense-fleshed and enticingly sweet -- plus, they keep well and are available long after summer's bounty has dwindled. This velvety-rich soup gets added sweetness from a bit of maple syrup, and buttery crunch from toasted pecans. Delicious.
Heat the oven to 375ºF. Grease a large baking dish with olive oil, and roast the squash, cut-side down, for 45 minutes to an hour, until tender (it should offer no resistance when pierced with a fork).
Meanwhile heat one tablespoon of the butter in a very small pan over medium-low heat and, when it foams, fry the pecans for 3 minutes until they are golden and smell toasty. Set them aside.
Heat the remaining 2 tablespoons of butter in a soup pot over medium-low heat and sauté the onion until soft and translucent, but not browned, around 10 minutes. Use a large spoon to scoop the flesh from the peel of the squash and add it to the soup pot along with the broth.
Bring to a boil, lower the heat, and simmer the soup, partially covered, for 20 minutes, stirring occasionally.
Puree the soup using a hand blender, or in batches, using great caution, in a blender or food processor. Stir in the half and half, then add nutmeg, maple syrup, salt, and pepper to taste and reheat very gently. Serve garnished with the nuts.