Meet Jane, a skilled baker who underestimates the complexity of her own recipe.
She sets out to make a simple cake, but her underestimation of the ingredients leads to a batch of inedible, rubbery disks.
Her underestimation of the baking time results in a batch of burnt offerings to the culinary gods.
Her underestimation of the oven temperature causes the cakes to emerge from the oven looking like they've been sat in the middle of a nuclear reactor.
And her underestimation of her own abilities leads to her setting off the fire alarm, the sprinklers, and a few of her neighbors' windows.
Links to related underestimation techniques:
Overcompensation: When Less is More (Not Really)