To make the crust: In a small bowl, mix the sourdough discard and water until it’s combined. Set aside.
In the bowl of a stand mixer fitted with the paddle attachment, add the flour, and cane sugar. Turn on low for two to three rotations to combine the dry ingredients.
Remove the butter from the fridge and chop into small cubes. The smaller the cubes, the flakier the crust: Cut the stick of butter into four and then chop into small cubes from there. Add the cold, cubed butter to the flour mixture.
Turn the mixer on low and slowly start to incorporate the ingredients. Gradually turn the mixer to medium speed. Once the butter mixture looks like wet sand, immediately add in all the sourdough and water mixture. As soon as the dough comes together, stop the mixer.
Have a piece of plastic wrap ready and form it into a disk and wrap in plastic wrap. Allow to cool in the fridge for at least 4 hours or overnight.
Preheat the oven to 350°F. Grease a 9-inch pie pan well with butter.
Remove the pie dough from the fridge. Remove the plastic wrap and place on a floured surface. Roll out the into a disk that is ¼-inch thick, it should be about 11-inches in diameter. Place the pie dough into the pie pan and press lightly to form against the pan. It should be large enough that the dough folds right over the top of the pan.
Roll the excess dough into the pie pan so it’s even with the edges of the pie pan. Flute the edges by using your thumb and index finger of your right hand to pinch the rolled edge of dough and push your index finger of your left hand into it to create the “flute”. Continue around the entire pie to flute the edges.
Place a piece of parchment paper into the pie pan and form it to the sides. Add rice or pie weights and parbake for 20 minutes. Remove the parchment paper and weights and bake for another 5 minutes. Press down the crust if it bubbles up in the middle.
To make the filling: In the bowl of a stand mixer fitted with the paddle attachment, add the pumpkin, heavy whipping cream, light brown sugar, and sourdough discard. Mix on low until combined.
With the mixer still on low, slowly add the cornstarch while still mixing, this will help prevent it from clumping. Add the pumpkin spice and continue to mix until combined.
Pour the filling into the pie crust. Fill only to right below the fluted edge! Even if you have more filling, do not use it if it’s too full as this will result in an exploded pie! If you have extra filling, add into small soufflé cups and bake along with the pie!
Place the pie (and soufflé cups) onto a baking sheet and bake for 32 to 36 minutes or until the pie looks somewhat set, it may still be a little jiggly in the middle. Allow to cool completely, at least 6 hours, preferably overnight. (Little soufflés may be done earlier if you have them.)
Allow to cool completely, at least 4 hours or overnight.
To make the whipped cream: In the bowl of a stand mixer fitted with the whisk attachment, add the heavy whipping cream, cane sugar, and vanilla extract. Mix, starting on low to avoid splattering, and gradually increase speed as the mixture thickens until you’re at full speed. Whisk until stiff peaks form.
Top pie with whipped cream and chopped pecans.