A week in advance, I sculpted the figures and trash cans from gum paste so they would have time to dry. The details of Joker and Batman were hand painted. Each building was made from six 8″ square cakes. One was strawberry, the other white.
For each building, I first leveled and stacked 3 cakes, placed plastic dowels in those, put a cake board on top and added the other 3 layers. I put 2 wooden skewers in each one to hold them steady. I then tinted some homemade fondant moss green and some dark gray. I rolled these out onto brick impression mats and put them around the sides of the cakes. The tops were covered in dark gray fondant. To dirty them up a little, I used edible brown dust on the green building and black dust on the gray one. I then made some light gray fondant to make the corners and edges of the buildings, as well as the garage door, steps and an air condition window unit.
I tinted some fondant light yellow to make the windows and door. I tinted some light brown to surround the windows and garage. I used some of the leftover dark gray to make the door frame and the brick decoration on the green building. I then tinted some black fondant to make the trash bag and covered the cake board in it as well.