Combine all ingredients in a saucepan over medium heat. Whisk briskly as mixture cooks until it snaps together as a slime — about 2 minutes. (Grown-ups only for this step)

Remove pan from heat and transfer pumpkin pie slime to a cutting board or nonstick silicon mat dusted with cornstarch. Turn slime with a spoon as it cools, adding about 1 Tablespoon of cornstarch.

When slime is cool enough to handle, finishing mixing by hand. You're ready to play!