Preheat the oven to 350 degrees. Lightly grease a 9-by-13-inch baking dish with baking spray. Line the bottom and long sides with parchment paper, leaving an overhang on each side to make removal easier. Spray again with baking spray. Set aside.

In a medium bowl, whisk together the flour, baking powder, and salt. Set aside.

Create a double boiler by placing a large heatproof bowl over a pot of simmering water. Add the chopped chocolate, butter, and oil. Stir frequently until everything is melted and smooth. Remove the bowl from the heat. Add both sugars and whisk until well combined. Add the eggs and vanilla; whisk until the mixture is glossy, about one minute. Stir in the dry ingredients just until combined. Be careful not to overmix.

Pour the batter into the prepared pan and smooth the top with a spatula. Arrange the pecan halves evenly over the batter.

Bake for 40 to 45 minutes or until a toothpick inserted into the center comes out with a few moist crumbs. Avoid overbaking to keep the brownies fudgy. Transfer the pan to a wire rack and let the brownies cool completely.

To make the caramel layer, place the caramels and heavy cream in a microwave-safe bowl. Microwave in 30-second intervals, stirring between each, until the caramels are melted and the mixture is smooth.

Drizzle the caramel over the cooled brownies and let it set for about 30 minutes. Once set, drizzle with the melted chocolate. (You can melt the chocolate using the double boiler method again.) Immediately sprinkle with flaky sea salt.

Let the chocolate set fully, then cut the brownies into squares and serve.

Store the brownies in the refrigerator. Bring to room temperature before serving for the best texture.