1In 4-quart Dutch oven, heat enough salted water to cover potatoes to boiling. Add whole potatoes; cook 25 to 30 minutes or until fork tender. Drain.
2Meanwhile, if using wasabi powder, mix 1 tablespoon powder with 1 tablespoon water in small bowl; let stand 5 minutes.
3In large bowl, place drained potatoes. Using electric mixer on low speed, breaking up potatoes. Beat in melted butter and salt. On medium speed, beat in yogurt and wasabi until desired consistency.