Line a quart-size freezer-safe bowl and a freezer-safe 8-ounce measuring cup with plastic wrap. Fill each with ice cream. You may need to soften the ice cream first.
Fill a 9- by 13-inch freezer-safe pan with the remaining ice cream, smoothing the top. Cover all the containers with plastic wrap and place them in the freezer to set.
Cut the taffy into small triangles for beaks and feet. Tip: To prevent the taffy from sticking to the blades of the kitchen shears, wipe a dab of vegetable oil on them with a paper towel.
Line a cookie sheet with parchment paper.
Melt the chocolate chips in the microwave, then stir in the vegetable oil.
Dip three sides of a cookie into the chocolate and set it on the paper. Press on the eyes and the beak. Repeat with the remaining cookies. Allow the chocolate to set.
Wipe your kitchen shears with more oil, then cut each marshmallow into a square. You'll end up with six sticky sides.
Roll the blocks in the decorating sugar and set them aside.
Peel the plastic wrap off the ice cream. Place the ice cream from the bowl onto the cake.
For the entrance, remove the ice cream from the measuring cup and cut off a small slice. Place the remainder on the cake, cut side down. Use a spoon to scoop out an opening.