Can one tell the edibility of a mushroom by taste?
told that if you place a small piece of mushroom under the tongue and there is no burning or reaction within an hour, that the shroom is probably OK. Is this correct?
This idea for telling if a mushroom is poisonous is going to get you sick or dead. The only known safe way to tell if a mushroom is poisonous is to identify it to species.
Consider that the most dangerous toxins, the amatoxins in the deadly Amanitas, can show no effects whatsoever for 12 hours, and even in large doses take at least 4 hours to show effects. Based on your friend's idea you could munch down a whole bunch of Amanita phalloides (the mushroom which kills more people than any other), since they taste good and won't show any symptoms until it's too late.