Prep oven. Preheat the oven to 350°F (180°C) and position a rack in the center of the oven.
Combine wet ingredients. In a large mixing bowl, whisk together the granulated sugar, eggs, brown sugar, oil, and vanilla. 4 large eggs 1 ½ cups (300 g) granulated sugar ½ cup (100 g) packed light brown sugar ½ cup (120 ml) canola oil 2 teaspoons vanilla extract
Combine butter and chocolate. In a small saucepan on the stove, over low heat, melt and stir together the butter and chopped chocolate. Stir frequently to keep the chocolate from burning. Remove from the heat and stir in the cocoa powder, whisking to combine. ½ cup (1 stick, 113 g) unsalted butter 8 ounces semi-sweet or bittersweet chocolate ¼ cup (21 g) Dutch process cocoa powder
Add chocolate mixture to sugar mixture. Whisk the chocolate/butter mixture into the sugar/egg mixture until smooth and combined.
Add dry ingredients. Add the flour, baking powder and salt. Stir, using a spatula (or wooden spoon) in the dry ingredients until just combined. 1 cup plus 2 Tablespoons (160 g) all purpose flour ¾ teaspoon salt ½ teaspoon baking powder
Bake the brownie layer. Spread batter on top of the graham cracker crust. Bake for 43-47 minutes. If the crust is browning too much cover with foil or a pie shield. I liked the pie baked at 45 minutes (and still found it wonderfully gooey). Transfer the pan to a wire rack to cool completely. Before serving, make the meringue.