I have what I think is a mushroom cluster growing in my mulch covered flower bed. I cut one open and it looked like smoke or powder coming out of it. It has a stalk. Also, it was filled with green slimy weird stuff (almost like baby mess). What does this sound like? Are these harmful to animals or humans?
Without a photograph, I can't tell you what it would be for certain.
The description sounds like "Dead Man's fingers", Pisolithus arhizus, which is reported to have been eaten in Germany at one time. However, without a photo, I can't tell you for sure that what you found is poisonous or not.