Preheat oven to 350ºF.

Line the pizza pan with parchment paper and oil lightly; trim excess.

Mix brownie mix according to package directions and spread on the pizza pan.

Bake brownies for ten minutes and remove from oven.

Sprinkle top with marshmallows, M&M's and sprinkles and press down with your hand- the dough will be a little dry on top so you need to press it in, but if you put it on before baking at all the candies will melt too much.

Return brownies to oven and bake ten minutes more.

Cool ten minutes, then slide pizza on parchment to a wire rack to cool completely.

Heat the white cookie icing according to package directions and draw the spider web onto the pizza with it, using the web lines to define the pizza slices.

Carefully remove the black spider from the mold; put a little of the white icing on the underside and press it down where you like the spider to be on the pizza.

Let the icing dry for 45 minutes to set up.

Slice into pieces to serve.