Cut 7 thin slices from cucumber; reserve.
Cut remaining cucumber into 3/4-inch chunks.
Place half the cucumber chunks and 1/4 cup of the yogurt in blender container.
Cover and blend on high speed until smooth.
Add remaining cucumber, the salt, mint and white pepper.
Cover and blend until smooth.
Add remaining yogurt; cover and blend on low speed until smooth.
Cover and refrigerate at least for 1 hour.
Garnish with reserved cucumber slices.