Grease and parchment-line an 8×8-inch baking dish.
Place chopped chocolate in a heatproof bowl. Melt butter in a saucepan over medium heat, pour it over the chocolate, wait 5 minutes, and stir smooth.
Beat eggs and sugar on high until pale and light. Add vanilla and salt, mixing for 1 minute. Mix in the chocolate-butter mixture for 30 seconds, then fold in flour. Reserve 2 tsp batter.
Spread the remaining batter evenly in the prepared pan.
Whisk cream cheese, sugar, egg white, and vanilla. Place 9 Tbsp-sized dollops over the batter and shape them into ghosts with a spoon and bamboo skewer.
Pipe eyes and mouths with the reserved brownie batter. Bake at 350°F (175°C) for 35–40 minutes, until edges are lightly golden and the center is just set.
Cool completely in the pan, then lift out and cut into 9 squares.