I ended up getting mushrooms from this technique, but by the time it was ready, the temperature was too low for proper mushroom formation. I didn't realize the mushrooms needed heat for quite a while, and by the time I finally put a heating pad under them, they'd been sitting there for quite a while. They did grow mushrooms though, and quite a lot of them. The only problem was mushrooms only grew from the edge of the cake, not the bottom, which was the part that was face up. A lot of mushrooms ended up growing from the edge of the cake, but they were very crowded and didn't get that big. This method worked, but I think that overall it was easier to use jars.