Wash the oranges thoroughly, cut into pieces (leave peel on), and remove seeds.
Simmer the oranges with 1 cup of water in a covered pan for 15 minutes. Ensure some liquid remains after cooking, or add a little more water if needed (the pectin will help thicken as it cools)
Add the chocolate to the pan and stir until melted.
Transfer everything to a blender and blend until smooth.
Pour into 6 small ramekins or 1 baking dish (7.5" x 6"), smooth the top, and refrigerate for 2+ hours.
Dust with cacao powder before serving.
