First, generously remove the peel from the oranges so that the white skin is also completely removed.
Separate the fillets, remove the seeds and collect the juice. Finely dice the flesh, mix with the preserving sugar and leave to infuse for one night with the lid closed.
Add the lemon juice and boil for 4 minutes until bubbly.
Stir in the liqueur, pour the jam into jars and seal tightly.