- Remove rind from the orange and set it aside.
- Peel and remove all the pith from the orange, then cut the orange into ¼ inch slices and refrigerate.
- In a food processor, puree the mango flesh and the orange rind until smooth.
- Strain through a fine sieve into a 1½ quart container.
- Add 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 and float an orange slice and mint leaves on top.