Preheat oven to 350°F (175°C). Grease and flour a 9x13 inch baking pan.

Cream together the softened butter and sugar until light and fluffy using an electric mixer.

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

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.

Gently fold in the chocolate chips (if using). Pour the batter into the prepared pan and spread evenly.

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

Let the brownies cool completely in the pan before frosting. Melt the white chocolate candy melts according to package directions.

Transfer the melted chocolate to a piping bag or a zip-top bag with a small corner snipped off. Pipe concentric circles of melted chocolate onto the brownies, starting from the center and working your way outwards. Then, using a toothpick or thin knife, drag lines from the center outwards through the chocolate circles to create the spiderweb effect. Allow the spiderweb to set completely before cutting and serving.