Preheat your oven to 350°F (175°C) to ensure even baking and perfect fudgy texture.
If using refrigerated crust, unroll and press into a 9-inch pie dish. If homemade, roll out and fit crust into dish, trimming excess. Poke holes in the bottom with a fork.
Melt unsweetened and semi-sweet baking chocolate with unsalted butter in a double boiler or microwave-safe bowl, stirring until smooth. Microwave in 30-second intervals if needed.
In a large mixing bowl, whisk granulated sugar, eggs, vanilla extract, and salt until combined. Gradually stir in melted chocolate mixture until smooth.
Sift in cocoa powder and all-purpose flour. Gently fold into the mixture until just combined, avoiding overmixing.
Pour brownie batter into the prepared pie crust and spread evenly. Bake for 30-35 minutes, until a toothpick comes out with moist crumbs but no wet batter.
Allow pie to cool at least 15 minutes before slicing. Serve warm with vanilla ice cream or whipped cream if desired.