Preparation

While the pie crust blind bakes, in a medium saucepan, combine the butternut squash and sweet potato. Add cold water just to cover, and cook over medium to high heat until very tender, 30 to 35 minutes. To check if the vegetables are done, carefully remove one of the chunks and press the flesh with the back of a fork—if it smashes easily, like a cooked potato, they are ready.

Drain, and let cool enough to handle, but not completely. It’s better to purée them while they’re still a bit warm—just like mashed potatoes. Place the squash and sweet potato in a food processor, and purée until smooth. You should have at least 1-1/2 cups of purée. Let cool completely before making the pie filling. (Note: The purée can be made in advance and stored in the refrigerator for up to 1 week or in the freezer for up to 2 months.)

In a medium bowl, whisk together 1-1/2 cups of the puréed butternut squash and sweet potato mixture, the evaporated milk, brown sugar, eggs, cornstarch, cinnamon, cloves, nutmeg, and salt. Strain through a fine-mesh sieve. After mixing and straining, the filling will develop a few bubbles on top. Let stand at room temperature until the bubbles dissipate, about 20 minutes.

Place a rack in the middle of the oven, and preheat to 300°F.

Fill the baked piecrust with the filling. Bake until the filling is firm around the edges and just a bit jiggly in the center, 1 hour to 1-1/4 hours. It is normal for the filling to puff a bit like a soufflé, but don’t worry, it will settle down once it cools. Remove from the oven. Let cool completely. Serve with softly whipped cream.