How do you pick good portobello mushrooms in the grocery store?

A portobello mushroom is nothing more than a fully mature cultivated white mushroom. Most people think it's an exotic mushroom, but it's just the regular white supermarket variety that's been allowed to grow to maturity. Back in the 80s, a clever marketing campaign coined the name "Portobello" to bestow a little more cache to the oft-overlooked grown-up creminis, and boost their popularity. Portobellos are actually creminis, which are the cultivated brown mushrooms you see in the supermarket. The difference between the three mushrooms is the maturity. The white button is the youngest and most mild tasting. If not harvested, it grows into a cremini, which is pretty similar to the white button in terms of size and taste, although it has a brown cap and is slightly deeper in flavor. Further growing of the cremini will yield the fully mature portobello, which has the most complex flavor. With this in mind, you simply choose portobellos the same way you'd choose any cultivated mushroom. ...  more