Preheat your oven to 350°F. Line an 8x8-inch square baking pan with parchment paper, leaving a 2-inch overhang on each end and butter the exposed sides.
In a large bowl over a pot with ½-inch of simmering water, stir together chocolate and butter until completely melted, smooth and glossy; set aside to cool about 5-10 minutes. You can also use the microwave.
Beat eggs with sugar in a large bowl using a whisk until pale, thick and fluffy. Beat in vanilla and salt then stir in warm chocolate mixture until evenly blended. Stir in flour until well incorporated and smooth. Pour batter into prepared pan and use the back of the spatula to smooth out the surface.
Bake until slightly puffed and a toothpick inserted someplace between the edge and the center comes out with a few moist crumbs, 20-25 minutes. Transfer pan to a wire rack and let cool completely.
For the topping, heat cream with corn syrup or honey in a small saucepan until it comes to a simmer. Remove from heat and add the chopped dark chocolate. Cover and let stand for 2 minutes then stir until smooth and glossy. Pour it over the brownies and spread in an even layer. Refrigerate for 1-2 hours until set. Drizzle with melted milk chocolate.