Dried Portabello Mushrooms Sliced. Few foods are as versatile as portabellas. Serve them as appetizers, entrees or side dishes. Substitute meat for portabellas. Use in lasagna, sauces, stews, risotto and more. There are an unlimited amount of recipes on the internet for portabellas, so that shows how popular they are. Reconstitute for 10-20 minutes in a cup of warm water per ounce of mushrooms. Watch them though and remove when they are done. They are best put into your dish that has liquid in them instead of reconstituting first. Just rinse them first. Once you reconstitute them, pat them gently and cook.