Butternut squash is the go-to vegetable for adding sweetness and substance to cool-weather cooking. Legendary French chef Alain Ducasse—whose restaurants around the world have earned him a staggering 17 Michelin stars—knows better than anyone how to make this everyday fall veggie shine.

But there's no big-kitchen wizardry required: Ducasse says the simplest way to showcase butternut's comfortingly tender texture is to slice the squash open lengthwise, remove the seeds, and then bake until fork-tender. "You can even toast the squash seeds and season to taste," Ducasse says. "Use them as a crunchy-textured garnish or as a snack."

Nor is his rich, hearty gratin much more complicated. Ducasse blends mashed butternut with earthy wild mushrooms and bits of bacon to balance the squash's sweetness. Our version substitutes more readily available beef stock for veal jus (which Ducasse uses), though the stock still delivers a savory umami note.

This month you can try Ducasse's version at his Parisian-style bistro, Benoit, in Manhattan.

Butternut Squash au Gratin with Wild Mushrooms and Crispy BaconHands-on: 50 min. Total: 1 hr. 50 min.1 tablespoon extra-virgin olive oil2 thinly sliced green onions8 cups finely diced peeled butternut squash, divided (about 4 pounds)½ teaspoon kosher salt, divided2 center-cut bacon slices4 ounces sliced chanterelle mushrooms4 ounces sliced shiitake mushroom caps1½ tablespoons chopped fresh sage¼ cup unsalted beef stock (such as Swanson)2 ounces Parmigiano-Reggiano cheese, grated and divided (about ½ cup)2 tablespoons part-skim ricotta cheese¼ teaspoon freshly ground black pepperCooking spray6 ounces oyster mushrooms, sliced

1. Preheat oven to 350°.

2. Heat a large skillet over medium-high heat. Add oil; swirl to coat. Add green onions; sauté 30 seconds. Add 6 cups squash; sauté 2 minutes. Reduce heat to medium-low, and stir in ¼ teaspoon salt. Cook, covered, 15 minutes or until tender. Increase heat to medium-high. Cook, uncovered, 2 minutes or until liquid evaporates, stirring frequently. Place squash mixture in a large bowl; mash with a potato masher or fork until smooth.

3. Cook bacon in a large nonstick skillet over medium-high heat until crisp. Remove bacon from pan, reserving drippings in pan; crumble bacon. Add chanterelles, shiitakes, and sage to drippings; sauté 8 minutes or until mushrooms are browned. Add stock; cook 3 minutes or until liquid almost evaporates. Add mushroom mixture, remaining 2 cups diced squash, remaining ¼ teaspoon salt, 1 ounce Parmigiano-Reggiano cheese, ricotta cheese, and black pepper to mashed squash mixture, stirring to combine. Spoon squash mixture into a broiler-safe 11 × 7--inch glass or ceramic baking dish coated with cooking spray. Cover with foil; bake at 350° for 1 hour. Remove pan from oven; discard foil.

4. Preheat broiler to high.

5. Combine bacon, remaining 1 ounce Parmigiano-Reggiano, and oyster mushrooms in a bowl; sprinkle over gratin. Broil 6 minutes or until lightly browned. Let stand 5 minutes before serving.

SERVES 8 (serving size: about 1 cup)CALORIES 163; FAT 5g (sat 1.9g, mono 1.9g, poly 0.4g); PROTEIN 6.9g; CARB 26.4g; FIBER 5.3g; CHOL 9mg; IRON 2.3mg; SODIUM 286mg; CALC 188mg