Cremini mushrooms (also referred to as cremino, common brown, and Roman), are commonly marketed as “baby bella” or “baby portobello” mushrooms because they are just that — a juvenile portobello mushroom.
These mushrooms are dark brown and firmer than the common white button mushroom. They have a smooth, rounded cap and a sheath of skin that covers their gills. When purchasing cremini mushrooms, check underneath the cap to see that the gills are covered. If they are, that’s how you know the mushroom is fresh.