Vichyssoise Soup (Carolyn)

3/4 lb leeks washed, sliced thin & lengthwise
1 medium onion
2 T butter
2 large potatoes peeled & diced (used Yellow Gold)
3 cups chicken stock made from scratch
salt to taste (none)
2 cups light cream (half & half)
dash of Tabasco (left out)
1 cup plain yogurt
Sauté leek and onion, do not brown. Add potatoes & stock cook about 30 minutes. Cool. Pour in blender with cream. Chill, add yogurt before serving & garnish.