Combine the apples, honeydew, water, sugar, orange juice, lemon zest and lemon juice in a 2-quart, heavy saucepan. (The amount of sugar varies depending on the sweetness of the honeydew. If the honeydew is very sweet, use 3/4 cup of sugar, but if it doesn't seem as sweet, increase the sugar to 1 cup.) Bring the mixture to a boil over medium-high heat, reduce the heat to medium low, and simmer uncovered for 20 minutes.
Remove the pan from the heat, add the basil to the pan and puree with an immersion blender, or in small batches in a blender (be sure to use caution when blending hot liquids in a blender). Transfer to a clean container and refrigerate until thoroughly chilled, at least 2 hours.
Stir the Champagne into the soup. Ladle into 6 small chilled bowls, and garnish with additional chopped basil and 2 Madeleines per serving. Serve immediately either as a first course or a dessert.
Yield: 6 cups