Line a sheet pan with parchment paper. Scrub and wash the oranges. Peel the oranges, leaving the pith on them. Save the fruit for a fruit salad. Cut the orange peels into thin (¼-in/5mm) slivers.
To remove the bitterness from the orange peel slivers, place them in a large saucepan and cover with water. Bring to a boil, reduce heat, cook for 10 minutes over medi