mangoes, very ripe
Remove the zest from the orange with a zester or grater and set it aside.
Cut a flat bottom on the orange, then remove all the peel and white pith from the orange with a small, sharp knife.
Cut the orange into 1/4-inch slices and refrigerate until serving time.
Peel the mangoes and remove the pits; puree the flesh with the orange zest in a food processor with the metal blade or in a blender until smooth.
Strain through a fine mesh strainer into a 1 1/2-quart refrigerator container.
Stir in the buttermilk, orange juice and honey to taste - The soup should be the consistency of whipping cream; if it is too thick, add more buttermilk.
Chill thoroughly up to 2 days before serving.
Just before serving, add lemon juice and more honey, if necessary; pour into chilled dishes.
Float an orange slice on top and garnish with a mint leaf.