Remove very thin strips of peel from 3 oranges. Cut strips into tiny slivers about 1-inch long and as thin as possible. Remove all remaining white pith and peel from oranges and discard. Bring water, sugar, cream of tartar and mace to a boil. Add slivers of orange rind and simmer until syrup is reduced to 1 1/2 cups. Place orange slices in serving bowl. Stir liqueur into syrup. Pour over oranges. Cool in refrigerator 4 hours before serving. Garnish with yogurt or coconut. Serves 6.