Preheat your oven to 350°F (175°C). Grease or line an 8x8-inch baking pan with parchment paper.

Combine semisweet chocolate and unsalted butter in a medium saucepan over low heat until melted and smooth.

Whisk granulated and light brown sugars into the melted chocolate mixture. Add eggs one at a time, mixing well after each addition. Stir in vanilla extract.

Sift together all-purpose flour, cocoa powder, and salt; fold into the chocolate mixture carefully.

Pour brownie batter into the prepared pan and bake for 20-25 minutes until a toothpick comes out with moist crumbs.

Cool brownies completely in the pan for about 30 minutes, then cut into small squares.

Heat heavy whipping cream in a small saucepan until it simmers. Pour over chopped semisweet chocolate in a bowl and stir until smooth.

Dip each brownie square into ganache, letting excess drip off. Sprinkle fleur de sel on top.