Preheat your oven to 350°F (175°C). Grease and flour an 8x8 inch baking pan.

In a large bowl, whisk together the melted butter and granulated sugar until 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. Do not overmix.

Spread the batter evenly into the prepared baking pan.

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

Let the brownies cool completely in the pan.

While the brownies cool, prepare the frosting: In a small bowl, whisk together the powdered sugar, milk, and vanilla extract until smooth. If the frosting is too thick, add a tiny bit more milk; if too thin, add more powdered sugar.

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

Using the black decorating gel, draw concentric circles on top of the white frosting, starting from the center and working outwards.

Drag a toothpick from the center outwards through the black circles to create a spiderweb effect. Repeat this in several places.

Cut the brownies into squares and serve.