Preheat the oven to 350 degrees F. Line an 8x8 inch baking dish with parchment paper. In a medium bowl, mix together the butter, sugar, vanilla, and eggs until combined. Add the cocoa powder, flour, and coffee and stir until just combined. Stir in the chocolate chips, if using. Spread the batter evenly into the prepared pan. Transfer to the oven and bake for 20-25 minutes or until the brownies are just set. Let cool and then cut into 9 bars. Freeze for 15 minutes. Meanwhile, in a microwave safe bowl, combine the chocolate and coconut oil. Microwave on high for 30 second intervals, stirring after each interval until melted. Let cool 10 minutes. Dip each frozen brownie into the melted chocolate, using a fork to toss the brownie in the chocolate to coat. Remove and allow any excess chocolate to drip back into the bowl. Place on a parchment lined cookie sheet. Repeat with the remaining brownies. Freeze for 10 minutes. In a small bowl, mix together the powdered sugar, black dye (or charcoal), and 1 tablespoon water until combined, adding water if needed to thin. Add the frosting to a ziplock bag and snip a small portion of the corner off the bag. Remove the brownies from the freezer. Add a dot of frosting to each brownie and attach a candy eye. Decorate the spell books as desired. Let the frosting dry and then serve, or keep in and airtight container in a cool place for up to 4 days.