Preheat oven to 350°F. Line an 8x8 inch baking dish with parchment paper.
Place butter in a microwave safe dish and heat till melted. Add chocolate chips and whisk till smooth. Transfer chocolate to a mixing bowl.
Add flour, salt and sugar to the mixing bowl with the chocolate. Stir to just incorporate the flour. Add eggs, egg yolk, and oil. Mix until combined. Stir in the chocolate chunks.
Transfer batter to baking dish and evenly. Bake for 40 minutes. When tested with a toothpick the toothpick should come out clean from the center.
Allow brownies to cool for at least 30 minutes before frosting.
Using a fine tip black decorating frosting make to book details on the brownie. Finally, add the candy eyeball.