Step 1

Coat a 2 1/2-quart ovenproof bowl with cooking spray. Prepare the cake mix as directed; pour into the bowl. Bake at 325 degrees F until a toothpick comes out clean, about 1 hour. Let cool completely.

Step 2

Unmold the cake from the bowl and position rounded-side down. Using a long serrated knife, trim off the domed top to make the cake level.

Step 3

Use a small serrated knife to cut a circle into the top of the cake, about 3/4 inch in from the edge and 1 1/2 inches deep. Use your fingers or a fork to pull out the cake in the middle.

Step 4

Flip the cake over and place on a cardboard circle or plate lined with wax paper. Cover the rounded side with frosting, leaving the flat base unfrosted.

Step 5

Cut out a small cardboard circle and place on the unfrosted base. Flip the cake over onto another piece of wax paper.

Step 6

Frost the lip and the inside of the cake (the inside doesn't have to be perfect-it will be covered with ice cream). Transfer to the freezer until the frosting sets, 30 minutes.

Step 7

Dip an offset spatula in hot water and wipe dry; smooth out the frosting.

Step 8

Microwave the ice cream until softened but not melted. Scoop into the cavity of the cake and smooth with the spatula.

Step 9

Sprinkle the cereal on top and gently press into the ice cream. Freeze until firm, at least 2 hours. Add a spoon before serving.