Preheat an oven to 350°F and place a rack in the center of the oven. Lightly butter a 9" x 9" baking dish, line with parchment, then lightly butter the parchment. Leave some parchment overhang (see photo above), so you can easily pull the brownies out of the pan.

Add flour, fine grain sea salt and cocoa powder to a medium bowl, whisking to combine. Set aside.

Bring a large pot filled with 2 inches of water to a simmer. Set a heatproof bowl on top of the pot, but make sure the bottom of the bowl is not touching the simmering water. Add butter and chocolate to the bowl, stirring until melted and combined. Turn off the heat, but keep the bowl on the pot. Whisk white sugar and light brown sugar into the chocolate mixture. Remove the bowl from the pot and let cool to room temperature.

Add eggs to the chocolate mixture, whisking until just combined. At this point, switch from a whisk to a spatula. You want to avoid adding extra air to the batter. Add vanilla and stir until just combined. Gently fold flour mixture into the chocolate mixture until just incorporated. Do not overmix here. Pour brownie batter into the prepared baking dish.

Cook for 16 - 18 minutes, or until a toothpick inserted into the center of the brownies comes out clean. The texture should be on the cakier sider, not fudgey or gooey. The toppings are gooey, so you don't want goo on goo. Transfer the baking dish to a cooling rack, and let cool for 5 minutes before topping.

Drizzle the surface of the brownies with salted caramel sauce, then sprinkle an even layer of chopped pistachios and sea salt. Repeat the layers once more to ensure a decadent coating. Cut into 9 even squares and enjoy!