Step 1Heat the oven to 400 degrees. Cut the squash into quarters and scoop out the seeds. Brush the cut surfaces of squash with oil. Put the squash cut-side down on a foil-lined baking pan. Roast until the squash is fork tender, about 60 minutes.
Step 2Toast the pecans on a large baking pan until lightly browned, about 6 to 8 minutes. Set aside.
Step 3In a small heavy skillet, melt the butter over medium heat. Continue to cook, whisking until the butter turns nut brown, 4 to 5 minutes. Mix the pecans with 1 teaspoon of the browned butter and the sea salt.
Step 4Heat the broiler. Turn the squash quarters upright with the skin side down. Drizzle each baked squash quarter with 1 teaspoon maple syrup. Put the squash under the broiler until the edges of the squash are slightly charred and the syrup has a nice glaze, 3 to 4 minutes.
Step 5Drizzle 1 tablespoon of the browned butter over each squash quarter, then sprinkle the nutmeg, toasted pecans and a little fleur de sel on the quarters and serve.