Why does this happen? After several days of research, I have compiled a list of the most common reasons this happens:
- the cake is too moist
- underbaking - increase baking temperature slightly (375 degrees)
- too much oil or butter in the recipe (oil-based recipes tend to do this less than butter) - can also use sour cream or plain yogurt
- liner issues - waxy or foil?
- overfilling liners & the batter gets stuck on the muffin pan
- cooling in the pan - take them out right away
- too much moisture in the storage container - cool cupcakes thoroughly