Preheat your oven to 350°F. Line two muffin tins with paper liners. Set aside.
Cake: In a large bowl, mix together the sugar, flour, cocoa, baking powder, baking soda and salt until fully combined.
Add in the eggs, milk, oil and vanilla, mixing until fully incorporated.
Stir in the boiling water. The batter will be very thin..
Scoop the batter into the muffin tins, around 3/4 full. Bake in the preheated oven for 14 – 17 minutes or until a toothpick comes out with some moist crumbs, but no liquid.
Let cool for 5 minutes in the pans, and then turn out onto a wire rack to cool. Let cool completely before frosting.
Frosting: In a large bowl, cream together the butter and the cream cheese until light and fluffy. Mix in the icing sugar 1 cup at a time until fully incorporated. Mix in the vanilla, cinnamon, and icing color if using. Pipe onto cooled cupcakes.
Spiderwebs: In a microwave safe bowl, melt the chocolate in 30 second intervals, stiring until the chocolate is melted. Pour the chocolate into a large freezer bag. Place some wax paper on a baking sheet. Cut the end off of the freezer bag, and pipe the chocolate onto the wax paper, creating your spider webs. Freeze until hard, then place on the cupcakes.