Heat oven to 350°F. Line an 8-inch square pan with parchment, leaving overhang. Lightly grease.
Warm the caramels with heavy cream in a small saucepan over low heat. Stir until smooth. Set aside.
Whisk melted butter with granulated and brown sugars in a large bowl until glossy.
Whisk in the beaten eggs and vanilla until the mixture looks thick and smooth.
Sift in flour, cocoa, salt, and baking powder. Fold just until combined. Stir in chocolate chips.
Spread about half the batter in the pan. Smooth the top with an offset spatula.
Drizzle on half the warm caramel. Dollop remaining batter over, then swirl gently with a knife.
Top with the remaining caramel in thin ribbons. Avoid touching the edges to reduce sticking.
Bake 28–32 minutes, until the center is just set and a tester shows moist crumbs.
Cool in the pan on a rack for at least 1 hour. Sprinkle flaky salt, then lift out and slice.