Combine all dressing ingredients into a mason jar or shaker of some kind. Shake until well combined. Set aside or refrigerate until ready to use.
Toast the hazelnuts in a small skillet over medium heat. It will take about 5 minutes but keep an eye on them, and stir occasionally, once you can smell them, they're done!
Arrange sliced fennel and citrus slices on serving plates. Top with toasted hazelnuts and shredded mangecho cheese. Garnish with fresh sliced basil and fennel fronds (the little green feathery tops). Drizzle with desired amount of champagne vinaigrette.
If you have a hard time finding champagne vinegar (which I did) you can substitute white wine vinegar. You can buy it online, or I've seen it at World Market, but generally not at your everyday grocery store.
See blog post for fennel slicing tips and health benefits!