"Mushrooms containing psilocybin are available fresh or dried and are typically taken orally. Psilocybin (4-phosphoryloxy-N,N-dimethyltryptamine) and its biologically active form, psilocin (4-hydroxy-N,N-dimethyltryptamine), cannot be inactivated by cooking or freezing preparations. Thus, they may also be brewed as a tea or added to other foods to mask their bitter flavor. The effects of psilocybin, which appear within 20 minutes of ingestion, last approximately 6 hours."
NIDA InfoFacts, "Hallucinogens: LSD, Peyote, Psilocybin, and PCP" National Institute on Drug Abuse (Bethesda, MD: National Institutes of Health, June 2009)