Prep the squash - Preheat the oven to 400℉, convection roast setting. Cut the squash in half, and scoop out the seeds. Spray the cut side of the squash with olive oil and place cut side down on a baking sheet. Once the oven is pre-heated, roast the squash until tender, about 20 minutes. Scoop the flesh of the squash out of the shells and mash it with a fork. Decrease the oven temp to 375℉.
Make the pie filling - Add the mashed squash, the eggs, 2 teaspoon of vanilla, ½ cup maple syrup, and 1 cup of evaporated milk to your blender jar, and blend until smooth. In a separate bowl, whisk together 2 T brown sugar, 1 T cornstarch, and 2 teaspoons of pumpkin pie spice. Add this to the blender with the wet ingredients and blend to incorporate.
Fill the piecrust(s) and bake - Pour the pie filling into your parbaked pastry shell(s) or crust(s). Bake for 50-60 minutes, or until the filling is set. Rotate the plate(s) halfway through the baking time to ensure even baking.
Garnish and cool before serving - Sprinkle the pie(s) with Maldon sea salt and decorate with whole walnuts or pecans (if using). Let the pie(s) cool completely before serving.