Make the pie dough. In a large bowl, combine 1¼ cups of all-purpose flour and ¼ teaspoon of fine grind sea salt. Grate ½ cup of very cold salted butter on the large holes of a box grater directly into the flour. Toss with your hands until every strand of butter is coated with flour.

Lightly break the butter up into small pebbles, tossing as you go. Do not work it into the flour. You want visible pieces of butter, because that is what gives you a flaky crust at the end.

Pour ¼ cup of cold tap water over the top and toss with a small spatula just to distribute it. Do not try to bring the dough together yet. Refrigerate for 5 minutes so the flour absorbs the water and the butter firms back up.

Mix with the spatula until the dough is almost together, then squeeze it with your hands, flipping and picking up loose flour as you go, until it forms a ball. This takes about 2 minutes. Resist adding more water unless the dough will not come together at all.

Turn the dough out onto a cutting board, press the rest of the loose flour in, and tidy it into a disc. A few cracks are perfectly fine, but you do not want it splitting wide open. Wrap it in plastic wrap and refrigerate for 30 minutes. Do not skip this rest.

While the dough rests, place a baking tray upside down on the middle rack and preheat the oven to 500℉/260℃ for 30 minutes. Chop 6 ounces of chocolate into small pieces. In a small bowl or measuring cup, whisk 3 room temperature eggs with 1 teaspoon of vanilla extract and ¼ teaspoon of fine grind sea salt, then set them aside at room temperature. Do not refrigerate them.

Flour a clean, dry counter generously and roll the dough out from the center to about ¼ inch thick, flouring and flipping it as you go. The flour stays on the surface of the dough and is never worked into it. Roll it well past the width of a 9-inch pie plate. If your kitchen is warm and the dough softens, wrap it and put it back in the refrigerator for a few minutes.

Make sure the dough lifts cleanly off the counter, then drape it into a 9-inch pie plate and settle it in without stretching. Trim the excess, leaving about an inch of overhang. Fold the overhang under and press it against the lip of the plate to build a little ledge all the way around, then crimp it with your knuckles. Refrigerate the shaped crust for at least 10 minutes, until it feels stiff and cold.

Brush about 1 teaspoon of cocoa powder over the bottom of the chilled crust. Line the crust with a piece of parchment that sits in the bottom and comes up the sides a little, leaving the corners long enough to use as handles. Pour in about 1 pound of dried beans, keeping them on the parchment, and push them out toward the crimped ledge so the sides set without puffing.

Make the filling. Melt ½ cup of salted butter in a saucepan over medium heat. When it is about halfway melted, add ½ cup of granulated sugar and ½ cup of packed light brown sugar and stir to combine. Add the chopped chocolate, stir it in, then turn the heat down to medium-low and gently melt the rest. Turn the heat off as soon as the chocolate is fully incorporated.

If the mixture looks like it is separating partway through, keep whisking. It comes back together as the rest of the chocolate goes in. Do not cook the sugar smooth. The filling should still feel grainy, which is what gives this pie its crackly brownie top. The finished filling will be noticeably thicker, about the consistency of a thickened pudding.

Pour the filling into the parbaked crust and bake on the middle rack at 350℉/180℃ for 25 minutes. The top should look set, with just a slight jiggle in the center when you nudge it, the same way a cheesecake does. Small bumps on the surface settle as it cools. Do not disturb the crackly top.

Let the pie settle at room temperature for about 15 minutes, then refrigerate it for at least 4 hours. Bring it out of the refrigerator at least 1 hour before serving so it slices cleanly and comes back toward room temperature.

Make the Chantilly cream. Whip 1 cup of heavy cream with 1 teaspoon of vanilla extract and 2 tablespoons of powdered sugar until it holds a peak. Using a large open star tip, pipe it around the edge of the pie only, taking it all the way out to the crust. Leave the brownie top showing.

Shave a little bittersweet chocolate over the cream with a vegetable peeler so you get curls rather than gratings. Cut the slices on the smaller side, because this pie is very rich.