In small glass, stir together ice water and vinegar. In bowl of stand mixer fitted with paddle attachment, blend flour, sugar and salt on low speed until well combined. Add butter and beat on medium speed 1 to 2 minutes or until butter is broken into smaller flakes and incorporated with the flour. With mixer on low speed, slowly stream in water and vinegar mixture until all water is incorporated.

Pour mixture onto clean work surface and form into a disc. If mixture is still too crumbly to do this, gently fold in additional cold water with your hands, 1 tablespoon at a time, just until dough holds together. Wrap dough in plastic wrap and refrigerate at least 1 hour or up to 1 day.

Place dough on lightly floured work surface and use floured rolling pin to roll dough into an 11-inch circle, rotating dough frequently. Gently press dough into 9-inch pie pan. Trim any excess dough, leaving about a 1-inch overhang, and then crimp the edge of the dough with your fingers. Return to refrigerator at least 30 minutes.

Meanwhile, preheat oven to 375 degrees F. Remove pie crust from refrigerator and line crust with parchment paper. Fill with pie weights, dried beans, or rice. Transfer to oven and bake 25 to 30 minutes or until edges of crust just begin to brown. Remove the parchment and pie weights and continue to bake 10 to 20 minutes longer, or until crust is light golden brown all over. Remove crust from oven; reduce oven temperature to 350 degrees F.

In bowl of stand mixer fitted with whisk attachment, beat eggs, granulated sugar and brown sugar on high speed 3 minutes or until light and fluffy. With mixer on low speed, slowly add chocolate mixture until all of chocolate mixture is incorporated. Add flour, cocoa powder and salt and gently fold with a spatula until just combined.

Pour brownie batter into pre-baked pie crust. Transfer to oven and bake 20 to 25 minutes or until brownie batter is just set. Transfer to cooling rack and allow pie to cool before cutting into slices.