Preheat your oven to 350°F (175°C). Grease and flour a 9x9 inch baking pan, or line it with parchment paper.

In a large bowl, whisk together the melted butter and granulated sugar until well combined.

Beat in the eggs one at a time, then stir in the vanilla extract.

In a separate bowl, whisk together the flour, cocoa powder, baking powder, and salt.

Gradually add the dry ingredients to the wet ingredients, mixing until just combined. Be careful not to overmix.

Fold in the chocolate chips.

Pour the batter into the prepared baking pan and spread it evenly.

Bake for 25-30 minutes, or until a toothpick inserted into the center comes out with moist crumbs attached.

Let the brownies cool completely in the pan on a wire rack.

While the brownies are cooling, prepare the spiderweb frosting. In a medium bowl, whisk together the powdered sugar, milk, and vanilla extract until smooth. If the frosting is too thick, add a little more milk, a teaspoon at a time. If it's too thin, add more powdered sugar.

Divide the frosting into two small bowls. Leave one bowl white and add the black food coloring to the other bowl, mixing until evenly colored.

Once the brownies are completely cooled, spread the white frosting evenly over the top.

Transfer the black frosting to a piping bag fitted with a small round tip (or a zip-top bag with a corner snipped off).

Pipe concentric circles of black frosting onto the white frosting, starting from the center and working your way outwards.

Using a toothpick or a skewer, drag lines from the center outwards through the black circles to create the spiderweb effect.

Cut the brownies into squares and serve.