2 tablespoons unsalted butter
1 medium butternut squash (about 1 ½ pounds), halved and seeds removed
½ cup (156 grams) maple syrup
⅓ cup (71 grams) light or dark brown sugar
½ cup (60 grams) heavy cream
1 teaspoon vanilla extract
2 large eggs
2 teaspoons ground cinnamon
1 teaspoon ground ginger
¼ teaspoon ground cloves
¼ teaspoon ground allspice
½ teaspoon fine sea salt
1 pie crust, par-baked in a No.8 Field Skillet (instructions here)
Preheat the oven to 375°F with the rack in the lower third of the oven. Place the butter on a baking sheet and place in the oven until the butter is melted, 3 to 5 minutes. Move the baking sheet back and forth to coat the base of the tray evenly with butter.
Place the butternut squash halves cut side down on the buttered baking sheet and move around to coat the surface well with butter. Roast until the squash is very tender, 40 to 45 minutes. Use tongs to gently turn the squash over on the baking sheet, and spoon any remaining butter over the squash, letting it collect in the place where you scraped the seeds away. Let it cool until it’s easy to handle. You’re aiming for 2 cups of squash (save any excess for another purpose). Transfer the squash to a food processor or blender (or a medium bowl if you plan to use an immersion blender).
Add the maple syrup, brown sugar, cream, and vanilla and blend the mixture until smooth. Transfer to a medium bowl, and whisk in the eggs, cinnamon, ginger, cloves, allspice and salt.
Gently pour the custard into the cooled par-baked crust. Transfer to the oven, and bake until the pie is set around the outside, but slightly jiggly in the center and the crust is deeply brown, 35 to 40 minutes.
Let the pie cool to room temperature in the skillet, then refrigerate the pie for at least 1 hour before serving.