Flour a workspace and roll out the pie crust into a 10” circle, rotating as needed and flipping the crust over to ensure it isn’t sticking to the counter.
Cut off the edges so there’s an even 1” overhang. Press the dough into the bottom of the pan.
Fold the edges under and all around then crimp (with a fork, pressing the fork into the edge) or flute the crust: use the thumb of your dominant hand and your fingers on the other hand to pinch the crust into a triangular shape (see video!).
Set the pie shell in the freezer to chill for 30 minutes.
Preheat the oven to 375 F.
Lay two sheets of aluminum foil, criss crossed, over the pie then fill the pie with pie weights or dried beans.
Bake the pie (this is the par-bake) for 30 minutes.
*When there’s about 20 minutes left, start making the brownie batter.
In a large bowl, add the cold butter. Set in the microwave for 1 full minute at 100% power.
The butter will be mostly melted, add the sugar to the bowl and, using a hand mixer, beat the mix for 30 seconds.
Set the bowl back in the microwave for 60 seconds.
The sugar/butter mix should be hot to touch. Add the cocoa and beat until the mix thickens, about 30 seconds.
Add the vanilla and salt, then add the eggs, one by one, while beating. Beat the batter for a good 60 seconds on medium speed.
Switch to a rubber spatula and add the flour and chopped chocolate. Stir to combine.
When the pie is done par-baking, take it out of the oven and use the foil to lift out the pie weights. The crust should be slightly brown on the edges and still doughy and soft in the center and on the sides.
Use a fork to dock the crust at the bottom of the pan. Pour in the brownie batter.
Lower the oven temperature to 350 F. Bake the pie for another 35 minutes, or until the center puffs up. If you take it out as soon as it puffs up, the texture will be on the fudgy side (less firm) if you leave it another 5-7 minutes after it puffs it will have the texture of a brownie.
Let the pie cool for an hour at room temperature. Top with whipped cream (recipe above) or serve with ice cream.