For the watermelon-apple compote, peel apples and melon, remove seeds and cut into bite-sized pieces. Place in an unperforated steamer basket with juice and zest of half a lemon, whole cane sugar and water.
Wash, pat dry and chop the mint and lemon balm. Add half of the herbs to the fruit and steam at 100° C for 7 minutes.
Let cool and sprinkle the compote with the remaining herbs before serving.