Make the pie dough:

1. In the bowl of a food processor, pulse the flour, sugar, and salt together. Cut the butter into small pieces, then add to the food processor. Pulse at 1-second intervals until butter is the size of peas—should be about 10 quick pulses. Add the ice water and pulse again about 10 times until the mixture is crumbly but holds together when pinched. Lay a clean tea towel on a work surface. Dump the crumbly dough mixture into the center of the towel. Grab the four corners of the towel together and twist to create a beggar’s purse, pressing the dough into a round. Use your hands to pack and flatten the round. If time permits, chill the dough for 30-60 minutes before proceeding, or better for 12 to 24 hours.  
2. On a lightly floured work surface, roll out the dough into a 13- to 14-inch round. Use as much flour as needed to prevent the dough from sticking, and every few rolls, flip the dough over. Transfer it to a 9-inch pie plate (be sure your pie plate is at least 2 inches tall). Trim dough that hangs over by a lot — leave at least an inch over hanging; you may not need to trim everywhere. Tuck the overhanging dough behind itself; then use your fingers to crimp the edge into a fluted pattern — video guidance here. Save the scraps in an airtight container in the fridge for another use. 
3. If time permits, chill the dough in the fridge until firm, about 30 minutes.

Parbake the dough: 

1. Heat your oven to 425ºF. If you have a Baking Steel or pizza stone, place it on a rack in the lower third of your oven. Lay a sheet of parchment across the pie plate and pour pie weights or dried beans or rice into the center until they reach the top of the pie crust. Use your hands to press the weights down and fit them into the edges of the fluted crust.
2. Transfer the filled pie crust to a parchment-lined sheet pan and transfer to the oven for 15-20 minutes or until the edges are just beginning to color — do rely on the visual cues here. It sometimes takes my crusts a little longer to take on that light color at the edges.
3. Remove the pan from the oven and carefully remove the pie weights or dried beans (which you can use again and again — let them cool completely; then transfer to a storage bag). Return the pan to the oven for another 2 to 3 minutes — it should take on only the slightest bit of more color all around. 

Fill and Bake the Pie:

1. Preheat your oven to 350°F.
2. Make the filling: In a large bowl, whisk together the maple syrup and melted butter. Add the cornmeal, brown sugar, and salt. In a separate medium bowl, whisk together the eggs, egg yolk, heavy cream, and vanilla until smooth. Whisk the egg-cream mixture into the maple syrup mixture and whisk again until very well combined or emulsified — this is important: several commenters have had issues with the mixture separating in the oven. 
3. Place the pie plate on a parchment-lined baking sheet. Pour the filling into the pie shell.
4. Transfer the baking sheet with the pie on it to the oven and bake for 45 minutes to 1 hour, until the edges are puffed and the center jiggles only slightly when shaken. It will look slightly underbaked when you remove it but it will continue to set as it cools. This consistently takes me at least 1 hour to cook. 
5. Remove the baking sheet from the oven and transfer the pie to a wire rack. Sprinkle generously with flaky sea salt. Let cool for 4 to 6 hours. Once fully cooled and at room temperature, slice, and serve. 
6. To make the whipped cream, beat the heavy cream with a wire whip or in an electric mixer until soft peaks begin to form. Sprinkle in a small handful of sugar (or don’t — I actually like this whipped cream without any sugar because the pie is on the sweet side) and a big pinch of flaky sea salt and beat until peaks begin to get firmer. Taste. Add more sugar (if using) and salt to taste. Beat until peaks begin to hold their shape or until they reach a texture you like — I like billowy, not-quite-stiff peaks. Store in fridge until ready to serve.
7. Store leftover pie, well wrapped in plastic wrap, or tucked into a jumbo ziplock bag, or under a pie dome, at room temperature for up to 3 days.