Cream the butter and sugars in a large bowl. Add eggs and mix to combine. Add vanilla and mix well.
Add dry ingredients, and stir until incorporated. Mix in chocolate chips.
Add M&M's to top for a pop of color.
Bake for 20-25 minutes.
Cool and remove from pan if desired. Use icing to pipe on the spiderweb design (create a cross, then diagonal lines, and connect the lines). Add plastic spiders for effect if desired, but remove before serving.