Using your double boiler melt the chocolate bar. Stir in the butter until melted and remove from heat.
Peel the oranges and tangerines and separate them into slices.
Meanwhile prepare a large baking sheet lined with wax paper.
Dip each orange and tangerine slice in the melted chocolate and using a spatula clean off any excess. Line them in one layer on the baking sheet.
Repeat the process until all oranges are covered in chocolate and sprinkle them with the red pepper flakes.
Refrigerate until the chocolate is set and serve chilled garnish with edible flowers or herbs.