Q.Regrowing Mushrooms From Ends.
I’m interested in regrowing button and cremini mushrooms. Your article only discusses regrowing oyster mushrooms. Can you give more information on growing the others? Also, you instruct to do layers of material and stem pieces. How would one access the pieces that are growing within the layers? Am I completely misunderstanding? I would love to learn how to do this, as storebought mushrooms around here are about $5 a pound now! Thanks.

Certified GKH Gardening Expert
It would be similar to growing oysters, but there are some very big differences to consider with mushrooms that grow on manure, such as cremini mushrooms.
Since you will not have the mushroom ends, being that they are removed before selling, the process will need to be done using tissue culture in sterile conditions. Personally, I have a flowhood, which is a laboratory grade ventilated workspace, which allows me to work with tissue culture readily.
If you do not have one of these, then it is going to be INCREDIBLY difficult. It isn't impossible, but it is not easy. It will require knowledge of agar work and sterile practice and fungal isolation from contamination.
There are other ways to try and re-grow them, but this will not be very reliable without the vigorous butt of the mushroom. This requires pulling mushrooms apart, without touching the inner meat, and spreading them into some aged manure. Keep this in a near perfect dark place and moist until you see growth IF you see growth at all that is not contamination.
Personally, if there isn't easy access to lab equipment and knowledge of sterile practice then this is going to be a frustrating and expensive task. I'm sure you can see why they are so expensive, at this time.
Oysters and wood loving mushrooms will be much easier, as they will not succumb to contamination as easily. They are much more forgiving.
Pholiota adiposa is a good one to start with. It is a wood-lover, fast, and forgiving. Just follow the steps in the article for an easy mushroom that can be similar in texture when it is young, with a more "woody" flavor, rather than the characteristics of the cremini from its growing medium.