Adjust pie crust into a deep dish pie plate.
In a large bowl, whisk together melted butter, sugar, vanilla, and salt.
Add the eggs, one at a time, whisking well after each addition.
Stir in the cocoa powder and flour, mixing until just blended.
Fold in the candy bars, M&Ms, and chocolate chips.
Pour the brownie batter into the pie crust - it will be pretty full.
Bake at 350 degrees for 40-45 minutes, or until a toothpick inserted near the center comes out mostly clean, with a few moist crumbs.
Remove to a wire rack to cool completely. Cut and serve.