Preheat the oven to 350F/177C convection (325F/162C conventional)and grease and line a 9"x13" pan with cooking spray and parchment paper.
In a heat safe bowl or a saucepan, melt the butter with the semi-sweet chocolate. Set them aside to cool while you get the rest of the ingredients together.
3/4 cup (170g) unsalted butter, 1 cup (6oz) semi-sweet chocolate chips
Combine the flour, cocoa powder and salt in a medium bowl.
1 cup (120g) all-purpose flour, 1/4 cup (25g) Dutch-process cocoa powder, 1/2 tsp salt
Use a whisk to combine the eggs, granulated sugar, brown sugar and vanilla until they're just barely combined; don't over-mix.
4 large eggs, 1 cup (200g) granulated sugar, 1/2 cup (95g) light brown sugar, 1 tsp vanilla extract
Slowly pour in the butter and chocolate mixture to the eggs and sugar, while whisking.
Use a sieve to sift the dry ingredients into the wet ingredients. Fold them together until they're just barely combined.
Pour the brownie batter into the prepared pan and bake for about 10 minutes.
Remove the brownies from the oven and allow them to cool for 10 minutes, while you mix the caramel pecan topping.
Caramel Pecan Topping
In a medium bowl, combine the melted butter and brown sugar. Add in the eggs and vanilla and whisk it until it's well combined.
1/4 cup (56g) butter, 1/2 cup (110g) light brown sugar, 3 large eggs, 2 tsp vanilla
Stir in the salted caramel sauce until it's fully incorporated. Add the pecans and toss them around until they're all fully coated.
Gently spread the mixture evenly over the brownies, transfer them back into the oven and bake for another 35 minutes, until the mixture on top is no longer runny.
Remove the brownies from the oven and top them with the chocolate chips- the chocolate will melt from the heat of the brownies. Use the back of a spoon to swirl the melted chocolate around, just before the chocolate dries, and when it's still a tiny bit tacky, top with sea salt flakes.
1/2 cup (3oz) chocolate morsels, pinch of sea salt flakes
Allow the brownies to cool completely before slicing.
Notes
For cleaner slices, refrigerate the brownie in the pan for 30-60 minutes and run your knife under hot water between every slice.