French:
* "pee-stoo" The "t" is silent, and the "ou" is pronounced like the "oo" in "moon".
English:
* "pis-too" Often pronounced with a short "i" sound like in "pit" and a short "o" sound like in "lot."
In culinary contexts, "pistou" typically refers to the French Provençal herb sauce, and the French pronunciation is more common.