Prepare a baking sheet with parchment paper and place a wire rack on top if available.
Wash and dry oranges and cut into thin round slices. Heat water and sugar in a large frying pan and stir till sugar dissolved. Add orange slices and let simmer for about 15 to 20 minutes till oranges slices turn slightly transparent. Transfer oranges to the wire rack and let dry for one day. If needed, let oranges dry in oven at 60° C.
Optionally melt chocolate in a small pot over medium to lower heat and dip oranges half way in. Place oranges back on wire rack to let dry. Store in an airtight container till serving.
Tip: Spread excess melted chocolate out on a baking sheet to a fine chocolate bar and use as desired.