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

In a medium saucepan over low heat, melt the semisweet chocolate and butter together until smooth.

Remove from heat and mix in the granulated and light brown sugars until combined.

Add the eggs one at a time, whisking after each addition. Stir in the vanilla extract.

Sift together the flour, cocoa powder, and salt. Fold into the chocolate mixture until combined.

Pour the batter into the prepared pan and smooth the top. Bake for 20-25 minutes, or until a toothpick inserted comes out with moist crumbs.

Allow the brownies to cool in the pan before transferring to a cutting board. Cut into squares or rectangles.

In another saucepan, bring the heavy whipping cream to a simmer over medium heat.

Remove from heat and pour over the chopped semisweet chocolate. Let sit for 2-3 minutes.

Stir until smooth and glossy.

Drizzle ganache over each petit four, allowing excess to drip off. Sprinkle with Fleur de sel.

Let ganache set for a few minutes before serving.