Heat oven to 350°F. Line an 8-inch square pan with parchment, leaving overhang. Lightly grease.
Melt butter and chopped bittersweet chocolate together until smooth. Let cool 5 minutes.
Whisk in granulated sugar and brown sugar until glossy and combined.
Gradually whisk in beaten eggs and vanilla until the batter thickens and looks shiny.
Sift flour, cocoa, espresso powder, salt, and baking powder over the bowl. Fold just until streaks disappear.
Fold in about 1 cup chocolate chips, reserving the rest for topping.
Spread batter evenly in the pan. Tap once to release air bubbles. Sprinkle remaining chips and flaky salt.
Bake 28–32 minutes, until edges are set and a toothpick comes out with a few moist crumbs.
Cool completely in the pan. Lift out using parchment, then slice into squares.
Notes
Variation: Swirl 1/3 cup warmed peanut butter or salted caramel over the batter before baking. Storage: Keep tightly covered at room temperature for 3 days, or chill for extra fudginess. Warm slices 10 seconds in the microwave for molten pockets.This recipe is an original creation inspired by classic Ultimate Chocolate Bomb Brownies flavors. All ingredient ratios and instructions are independently developed.